In recent years, advances in ancient DNA sequencing have redefined our understanding of human evolution, revealing that our species did not emerge in isolation but repeatedly interbred with close evolutionary relatives like Neanderthals and Denisovans.

Yet one of the field’s greatest mysteries has remained unanswered: What if some of our ancestors also encountered extinct human groups whose DNA has never been recovered from fossils? Now, a recent study published in Science suggests researchers may finally have found a way to detect those long-lost relatives.

Instead of relying on ancient bones or preserved genomes, researchers developed a powerful computational approach capable of identifying genetic traces of previously unknown archaic humans using only the genomes of living people.

Applying the technique to modern populations around the world, the researchers uncovered evidence that an unidentified “ghost” hominin contributed DNA to the ancestors of all living humans before the great migration out of Africa.

Researchers also found new evidence providing evidence for the existence of an even older “super-archaic” human lineage whose genetic legacy may survive today through Denisovan ancestry in Oceania.

“Admixture between modern humans and extinct hominins has shaped the genomes of present-day individuals, but reconstructing this history has been constrained by the scarcity of archaic samples and unadmixed outgroup populations,” researchers write. “We introduce TRACE, a reference- and outgroup-free approach that uses features of ancestral recombination graphs to identify archaic ancestry.”

Past research has sequenced only a handful of high-quality archaic human genomes, all from Eurasia. While those genomes have revealed that most people outside Africa carry roughly 1 to 2 percent Neanderthal DNA and that many Asian and Oceanian populations also inherited Denisovan ancestry, scientists have long suspected those known groups represented only part of humanity’s evolutionary history.

Previous genetic studies had hinted that modern humans, especially African populations, contained fragments of DNA from unidentified archaic relatives. However, because no fossil genomes exist for those populations, proving their existence has been extraordinarily difficult.

The new method, called TRACE, short for “TRacking Archaic Contributions via ARG Estimation,” takes a fundamentally different approach. Rather than comparing modern DNA against known Neanderthal or Denisovan genomes, it reconstructs ancestral recombination graphs. These enormous evolutionary family trees trace how pieces of DNA have been inherited over hundreds of thousands of years.

These ancestral graphs preserve signatures left behind when deeply divergent human lineages interbred. Such events create unusually long branches and distinctive genetic patterns that can persist in descendants for hundreds of thousands of years. By searching for those signatures, TRACE can identify archaic ancestry even when no reference genome exists.

To test the system, the researchers first ran extensive computer simulations modeling ancient human populations and known episodes of Neanderthal interbreeding. The method consistently revealed high accuracy while producing very low false-positive rates.

The team then applied TRACE to genomes from the 1000 Genomes Project, encompassing hundreds of individuals representing populations across Africa, Europe, Asia, and elsewhere.

The program successfully recovered well-established Neanderthal ancestry in Europeans and Asians, along with Denisovan ancestry concentrated primarily in Asian populations. More intriguing, however, was the discovery of an additional category of DNA that matched neither Neanderthals nor Denisovans.

TRACE identified between roughly 0.5 and 1.1 percent “ghost” ancestry across all modern populations examined. The genetic evidence suggests these segments originated from an unknown archaic human lineage that diverged from our ancestors roughly 830,000 years ago, before later contributing DNA to the ancestors of modern humans.

Perhaps most surprising was where that ancestry appeared.

Rather than being confined to African populations, as several earlier hypotheses proposed, the researchers found remarkably similar ghost ancestry in both Africans and non-Africans.

Most of the segments detected outside Africa were shared with African populations, suggesting the interbreeding event occurred before modern humans started dispersing across the globe roughly 50,000 to 70,000 years ago.

The findings point toward a previously unrecognized chapter of human evolution in which an unidentified human population mixed with the common ancestors of everyone alive today.

The researchers also explored where these ancient genetic fragments survive in the modern genome.

They found ghost ancestry spread across more than 70 percent of the accessible human genome, although it was far from evenly distributed. Some regions contained unusually high concentrations of ghost DNA, including genes involved in immune function and metabolism.

Even more unexpectedly, ghost ancestry persisted inside genomic regions previously believed to be largely devoid of archaic DNA.

These regions, known as “Neanderthal and Denisovan ancestry deserts,” have often been interpreted as places where natural selection eliminated archaic genetic variants because uniquely modern human versions proved advantageous.

The presence of ghost ancestry inside many of those same regions suggests the story may be more complicated. Rather than rejecting all archaic DNA equally, natural selection may have acted differently depending on which ancient human lineage contributed the genes.

The study also ventured even farther back in evolutionary time.

Focusing on genomes from Papua New Guinea, Vanuatu, and the Santa Cruz Islands, the researchers searched for evidence of “super-archaic” ancestry—genetic contributions from a lineage that diverged long before Neanderthals, Denisovans, and modern humans separated.

Previous studies had suggested Denisovans themselves may have inherited DNA from such an ancient population. TRACE now provides additional support for that hypothesis.

The team identified deeply divergent genetic segments embedded explicitly within Denisovan-derived DNA in Oceanian populations. Based on their analyses, those ancient lineages may have split from the ancestors of modern humans approximately 1.77 million years ago.

While the researchers stress this represents a conservative estimate of surviving super-archaic ancestry, the findings strengthen the idea that modern humans indirectly inherited DNA from a much older human lineage through Denisovan interbreeding.

The identity of both the ghost lineage and the super-archaic population remains unknown.

The ghost population may represent Middle Pleistocene human groups or African populations of Homo heidelbergensis that encountered the ancestors of modern humans before the Out-of-Africa migration. For the older super-archaic lineage, the researchers note that Homo erectus remains one plausible candidate given its estimated divergence time and broad geographic distribution.

Although the new method cannot yet identify specific fossil species, it provides researchers with an entirely new tool for investigating chapters of human evolution that may never yield recoverable ancient DNA.

Because DNA older than roughly one million years is extraordinarily unlikely to survive outside permanently frozen environments, computational approaches like TRACE are becoming increasingly important for reconstructing humanity’s deepest evolutionary history.

“We find evidence for at least one ghost introgression predating the OOA expansion that contributed ancestry to all present-day populations,” researchers write. “These results point to multiple layers of introgression—both direct and mediated through other archaic groups—shaping modern human genomes.”

The study, “Recovering signatures of archaic hominin introgression using ancestral recombination graphs,” was published in the journal Science.

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com 

Beneath the seemingly unbroken canopy of the southwestern Amazon rainforest lies evidence of one of the largest monumental landscapes ever discovered in the ancient Americas.

According to new research published in Nature, what archaeologists once believed were scattered ceremonial sites are instead part of an enormous precolonial civilization that may have changed vast stretches of the Amazon nearly 2,000 years ago.

Using airborne LiDAR capable of penetrating forest cover, an international team of researchers says they have identified hundreds of previously unknown earthworks, estimating that more than 20,000, and perhaps as many as 30,000, remain spread across southwestern Amazonia.

The findings dramatically expand the known scale of the so-called Aquiry civilization and suggest that millions may have inhabited the region during its peak nearly 2,000 years ago, forcing a reconsideration of how densely populated and intensively managed the ancient Amazon may have been.

“We also propose that the total human population of the area in 100–300 AD was 1.25–3 million people,” researchers write. “If similar results are found elsewhere in Amazonia, the total precolonial population density and its effect on the current Amazonian soil and forest structure, biodiversity, and even some modeling of the global climate should be re-evaluated.”

The study represents one of the most ambitious archaeological surveys ever conducted in the Amazon. Researchers flew more than 2,700 miles across the forests of Brazil’s Acre and Amazonas states using airborne LiDAR, a laser-mapping technology able to see through gaps in the dense treetops to produce detailed maps of the landscape below. Those maps revealed hundreds of geometric earthworks that had remained hidden for centuries.

The newly discovered structures include squares, circles, rectangles, and multilateral enclosures connected by roads and clustered into monumental complexes.

Some feature ditches up to 43 feet wide and more than 16 feet deep, with towering earthen embankments rising alongside them. Although a handful of these earthworks had previously been identified in deforested areas using satellite imagery, LiDAR revealed that those earlier surveys had dramatically underestimated just how many remained obscured beneath the forest.

One of the study’s most striking findings was that LiDAR scanning uncovered roughly five times more earthworks than satellite imagery had detected across the same landscapes.

In one survey block, researchers had previously identified only 30 structures using conventional imagery. Meanwhile, LiDAR revealed 156. Assuming similar results across the wider region suggests that between roughly 24,000 and 30,000 earthworks may exist within the estimated boundaries of the Aquiry civilization.

Those numbers alone would rank the region among the most monument-rich archaeological landscapes in the world.

For decades, archaeologists have debated whether much of Amazonia could have maintained large, complex societies before European contact. Prevailing interpretations portrayed much of the rainforest as environmentally limiting, capable of sustaining only relatively small and dispersed populations. However, more recent discoveries, including ancient cities in Bolivia and Ecuador, have steadily challenged that assumption.

Now, these latest findings suggest the region may have supported an even larger and more sophisticated society than researchers once imagined.

Rather than representing isolated ceremonial sites scattered through an otherwise untouched forest, the researchers argue the earthworks belonged to a civilization extending about 71,000 square miles, representing about three times larger than previous estimates of the Aquiry cultural area.

Many of the geometric enclosures appear not to have been permanent settlements themselves. Instead, researchers believe they served as ceremonial, political, and public gathering places where dispersed communities periodically assembled.

Similar patterns of temporary gathering centers are known from the Inca Empire, where populations converged for rituals, governance, and communal events despite living across broad landscapes.

Constructing these massive earthworks would have demanded sophisticated planning, organized labor, mathematical knowledge, and long-term social coordination. According to the study, some of these ceremonial centers remained in use for nearly 1,500 years, indicating remarkable cultural continuity across generations.

Estimating how many people actually lived within this landscape presented a separate challenge.

Rather than simply multiplying earthworks by a fixed population estimate, the researchers combined several independent lines of evidence. They examined radiocarbon dates to determine how many sites were occupied simultaneously, compared the earthworks with later mound villages built in the same region, incorporated ethnographic information from Indigenous communities, and evaluated the labor required to construct and maintain the monumental enclosures.

Their study indicates the civilization reached its greatest extent between approximately A.D. 100 and 300. During that period, somewhere between one-quarter and roughly 60 percent of the known ceremonial centers may have been active simultaneously.

Assuming each ceremonial center served communities of roughly 300 people, the researchers estimate the region’s population reached between about 1.25 and 3 million people during its peak. After accounting for earthworks that LiDAR may have missed beneath dense forest, they conclude the total could have been as high as 3.8 million.

Those estimates substantially exceed many previous reconstructions of southwestern Amazonia and imply population densities rivaling or exceeding some later historical agricultural societies.

Equally significant is what these discoveries reveal about how ancient Amazonians altered their environment.

The study points to fertile soils rich in nutrients, evidence of extensive cultivation of maize, squash, manioc, beans, peanuts, sweet potatoes, and chili peppers, as well as widespread management of Brazil nut groves and numerous economically important palm species.

Rather than exhausting the rainforest, researchers contend these communities actively managed forests, soils, and waterways throughout centuries, creating ecological legacies that remain visible today in the composition and biodiversity of Amazonian forests.

Present-day ecological studies have increasingly shown that many Amazonian forests long regarded as pristine wilderness actually bear the imprint of thousands of years of Indigenous landscape management. If similar densities of monumental earthworks are identified elsewhere across Amazonia, researchers argue that assumptions about precolonial population sizes, biodiversity patterns, soil formation, and even climate models may need substantial revision.

The work additionally underscores the key role of LiDAR in modern archaeology. Over the past decade, the technology has revealed hidden Maya cities beneath Central American jungles, extensive urban complexes in the Bolivian Amazon, and extensive settlements in Ecuador’s Upano Valley.

Nevertheless, researchers caution that important questions remain unanswered. The southeastern limits of the Aquiry civilization are still poorly understood because large portions of Rondônia have yet to receive comparable archaeological investigation. Dense vegetation also continues to obscure portions of the landscape, meaning many earthworks almost certainly remain undiscovered even after LiDAR surveys.

“These ancient achievements constitute an important legacy that is still observable in the soil, and the composition and biodiversity of the contemporary tropical forest,” researchers write. “This legacy should be fully considered in future studies of Amazonia, including climate modeling and sustainable land-use planning.”

The recent study, “Over 20,000 precolonial earthworks in the Southwest Amazonia,” by Martti Pärssinen et al., appeared in Nature.

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com 

For more than two millennia, astronomers have puzzled over a stellar mystery recorded by some of history’s greatest skywatchers. Hipparchus, Ptolemy, and the Persian astronomer al-Sufi—all separated by more than 1,000 years—each described Theta Eridani as one of the brightest stars in the night sky. Yet today, the previously celebrated star barely ranks among the more noticeable stars visible to the naked eye.

A new astronomical study published on arXiv suggests that those ancient observers may have unknowingly recorded an extraordinarily rare stellar event. The star system remained dramatically brighter than normal for roughly a millennium before fading back to its present appearance sometime between the 10th and 16th centuries.

If confirmed, the finding would be among the longest-lived stellar transients ever proposed, fusing modern astrophysics with historical astronomy to reconstruct an event spanning centuries rather than days or months.

The study combines historical star catalogs with state-of-the-art observations from the European Southern Observatory’s Very Large Telescope Interferometer (VLTI), high-definition spectroscopy, and NASA’s Transiting Exoplanet Survey Satellite (TESS).

Together, those observations allowed the researchers to reconstruct the architecture and evolutionary state of the Theta Eridani system and to propose a physical mechanism that could explain its mysterious ancient brilliance.

“The remarkable combination of orbital and stellar parameters hints that the historical brightening of Theta Eridani was due to a millenary transient phase,” researchers write. “This strengthens the case that the apparent brightening was real and not due to an error by three different ancient observers, as has been commonly claimed in the past.”

Today, Theta Eridani, also known by its traditional name Acamar, shines at approximately magnitude 2.9, making it a respectable but hardly spectacular star marking the end of the constellation Eridanus. Yet ancient records tell a very different story.

Hipparchus described it as an exceptionally bright star around 129 BC. Roughly 250 years later, Ptolemy ranked it among only fifteen first-magnitude stars in the Almagest, effectively placing it among the thirteen brightest stars visible in the night sky.

More than 800 years afterward, the Persian astronomer al-Sufi independently retained that same first-magnitude classification while revising the brightness estimates of many other stars toward values that closely match modern observations.

The sharp contrast between the historical accounts and Theta Eridani’s modest appearance today has made the star one of astronomy’s most enduring and compelling mysteries.

Researchers examined long-standing alternative explanations, including simple observational mistakes, copyist errors in ancient manuscripts, confusion with the much brighter star Achernar farther south, and even errors caused by atmospheric extinction near the horizon. One by one, they argue the evidence weighs against those explanations.

Theta Eridani would not even have been visible to the Greek and Arab astronomers because of Earth’s changing orientation over time. Likewise, statistical analyses of nearly 1,000 stars contained in the Almagest show that Theta Eridani represents the single largest discrepancy between ancient and modern brightness estimates, rather than part of a wider systematic mistake.

The historical trail eventually changes around the dawn of the Age of Exploration. By the late 1500s and early 1600s, after European navigators began mapping the southern skies, star catalogs consistently described Theta Eridani as only a third-magnitude star—essentially the same brightness observed today.

That suggests the bright phase had already ended.

To investigate whether Theta Eridani itself could plausibly have undergone such a transformation, the team turned to modern astronomical observations.

Rather than a single star, Theta Eridani consists of three stars. The primary component itself is a remarkably tight binary whose two stars orbit one another every 4.1077 days at a separation of just 0.083 astronomical units—roughly one-fifth the distance between Mercury and the Sun.

Using interferometric measurements from the VLTI, together with spectroscopy and precision photometry from TESS, the researchers determined that the two stars each contain just over twice the Sun’s mass and have swollen to approximately 4.3 and 4.0 solar radii.

Those enlarged sizes are significant because both stars have expanded to nearly 80 percent of the volume where gravity from one star begins pulling material toward the other, a region around a star in a binary system known as the Roche lobes. The close gravitational interaction also produces measurable ellipsoidal distortions that TESS detects as subtle, rhythmic brightness variations every orbit.

Researchers’ evolutionary modeling further revealed that the primary star occupies an unusually brief stage within stellar evolution, having only recently exhausted hydrogen in its core and begun transitioning into a subgiant. That evolutionary timing may be critical.

According to the researchers, Theta Eridani may once have possessed a much more elongated orbit. As the primary expanded, it could have begun overflowing its Roche lobe during each close approach, transferring material toward its companion and possibly generating an extended common envelope surrounding both stars.

Unlike the violent stellar explosions astronomers typically classify as transients, this proposed event would have evolved extraordinarily slowly. Instead of lasting weeks or years, the researchers suggest the envelope may have persisted for roughly a thousand years while gradually extracting orbital energy from the binary.

Because the surrounding envelope would have remained optically thick, it could have radiated from an area far larger than either star individually, making the entire system appear nearly ten times brighter than it does today.

Researchers’ calculations suggest that such an envelope could have reached roughly 20 times the Sun’s radius while needing only a tiny amount of encircling material, because that material would be continually replenished and slowly ejected over hundreds of thousands of orbits.

Importantly, researchers stress that this is still a proposed physical explanation rather than a demonstrated one. Modeling the detailed hydrodynamics of eccentric mass transfer and long-lived common envelopes remains beyond the scope of the current work.

Nevertheless, they argue that the unusual combination of orbital geometry, stellar evolution, and historical observations makes the scenario physically plausible.

The study of Theta Eridani also raises wider implications for time-based astronomy.

Modern astronomical surveys are exceptionally good at finding dramatic events that unfold over minutes, days, or years. A stellar brightening lasting centuries, or even a millennium, would be almost impossible to recognize within a human lifetime. Researchers suggest there may be other long-duration stellar transients hidden among ordinary-looking stars whose histories have been forgotten.

If their interpretation proves correct, some of humanity’s earliest astronomers may have unknowingly documented one of the most unusual stellar phenomena ever proposed—not an exploding star, but a binary system trapped in an exceptionally slow evolutionary episode which lit up the night sky for generations before quietly receding into obscurity.

“Although modern photometric surveys have had an observational coverage of a few years to a few decades rather than two millennia like Theta Eridani, they are sensitive to objects up to 14 magnitudes fainter than the naked eye limit,” researchers write. “Therefore, there could be unexplored or unexplained Theta Eridani-like transients that either brightened or faded in current data.”

The team’s new study, The Forgotten Bright Star: Theta Eridani as a Millenary Stellar Transient Observed by Hipparchus, Ptolemy and al-Sufi, is currently available on the arXiv.org preprint server.

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com 

For decades, Washington has assumed that military aid translates into political influence. If the United States provides the weapons, intelligence, training, and diplomatic backing that keep an ally fighting, conventional wisdom suggests it should also have considerable leverage over when, and how, that war ends.

Yet, a sweeping new analysis published by the Brookings Institution and authored by Dr. Dafna Rand, a senior fellow at Brookings, the Federation for American Scientists, and the Council on Foreign Relations, argues that the opposite has increasingly become true.

Whether in Ukraine, Gaza, Yemen, or Afghanistan, the U.S. has repeatedly discovered that sustaining an ally’s war effort is often far easier than steering its ultimate direction. Instead of conclusive victories followed by lasting peace, modern conflicts are increasingly settling into drawn-out stalemates, frozen conflicts, or recurring cycles of violence that resist outside pressure—even from Washington.

Dr. Rand’s report examines one of the defining strategic dilemmas confronting American foreign policy in the 21st century: why the world’s most powerful military and diplomatic actor has struggled to shape the decisions of partners whose war efforts depend heavily on U.S. support.

Drawing on more than 30 interviews with senior American officials involved in decision-making throughout four major conflicts, alongside hundreds of government documents, the analysis shows recurring patterns that appear independent of geography or the adversary involved.

“Wars, whether between or within states, are not ending in the 21st century,” Dr. Rand writes. “Frozen conflicts, on-again-off-again fighting, and stalemates have become the norm.”

Dr. Rand argues that this changing nature of warfare has profoundly changed the assumptions underpinning American security strategy.

Following the costly wars in Iraq and Afghanistan, Washington increasingly shifted toward supporting partners rather than committing large numbers of U.S. troops directly to combat. The expectation was that supplying allies with military assistance would provide the United States with considerable influence over battlefield strategy and political consequences.

Instead, Dr. Rand says that American leverage consistently diminishes as conflicts drag on.

One of the study’s central conclusions is that Washington and its partners frequently begin wars without agreeing on what victory actually means. At the outset of each conflict examined—including Ukraine’s defense against Russia, Israel’s campaign against Hamas, the Saudi-led intervention in Yemen, and America’s withdrawal from Afghanistan—American and partner governments shared broad objectives, though often failed to establish detailed political end states.

That omission, Dr. Rand argues, becomes increasingly costly as wars continue.

Early battlefield success frequently encourages partners to pursue more ambitious goals than originally envisioned. At the same time, Washington gradually becomes more interested in negotiated settlements as financial costs mount, domestic political support declines, and wider strategic priorities begin competing for attention.

According to Dr. Rand, many officials interviewed expressed regret that these conversations about political objectives, postwar governance, and acceptable settlement terms did not occur before military campaigns gained momentum.

The report also highlights an uncomfortable reality of modern alliances. Although the United States provides enormous military assistance, it does not exercise command over allied governments or their armed forces. As a result, disagreements naturally emerge over strategy, operational design, and acceptable risks.

Ukraine provides one of the clearest examples. Initially, Washington and Kyiv shared an overriding objective of preventing Russia from conquering the country. However, over time, American officials became increasingly divided over whether continued fighting or eventual negotiations better served long-term U.S. interests.

Some officials viewed prolonging the conflict as strategically beneficial because it weakened Russia’s military while strengthening Ukraine’s defense capabilities. Others believed diplomatic attempts should have begun earlier, particularly after Ukraine’s battlefield gains in 2022 created what they viewed as an opportunity to negotiate from a stronger position.

Dr. Rand notes that internal disagreements within the U.S. government complicated communication with Ukrainian leaders, in particular regarding expectations for territorial objectives and the role military offensives were intended to play in eventually creating conditions for diplomacy.

The Gaza conflict exposed a different, but related, collection of challenges.

Following Hamas’ October 7, 2023, attacks, President Joe Biden’s administration moved rapidly to reassure Israel of unshakable American support while simultaneously urging restraint based on lessons learned from America’s own post-9/11 military campaigns.

Dr. Rand concludes that Israeli leaders largely heard the reassurances while failing to fully internalize Washington’s accompanying warnings about civilian casualties, operational design, and the long-term strategic consequences of an extended campaign.

As the war progressed, American officials increasingly concluded that humanitarian concerns and mounting civilian casualties were not exclusively moral issues but strategic ones as well, arguing that prolonged destruction could ultimately strengthen Hamas’ long-term recruitment and undermine Israel’s own security objectives.

Despite this growing divergence, the report suggests Washington hesitated to use its available leverage aggressively, partly because of domestic political sensitivities surrounding support for Israel.

Another recurring finding centers on American public opinion.

Support for allies often begins overwhelmingly strong immediately after major attacks or invasions. But that support steadily erodes as wars lengthen, casualties mount, humanitarian problems increase, or questions come up regarding the conduct of partner governments.

Dr. Rand says this pattern appears across Yemen, Afghanistan, Gaza, and, increasingly, Ukraine.

Importantly, she argues this erosion can occur even when Americans continue believing the underlying cause remains just. Instead, fatigue over prolonged commitments, concerns about costs, or doubts regarding the likelihood of decisive success gradually reshape political calculations in Washington.

Those changing domestic dynamics, in turn, reduce America’s leverage abroad.

Once congressional debates begin questioning military assistance or public enthusiasm declines, allied governments recognize that Washington’s ability to maintain long-term support has become less certain.

Dr. Rand argues this weakens American bargaining power precisely when policymakers most need it.

Among the study’s most significant recommendations is that future administrations should treat leverage as a rapidly diminishing resource.

Rather than assuming influence will expand alongside continued military assistance, Dr. Rand contends the opposite usually occurs. The strongest opportunity to shape an ally’s political objectives exists during the opening weeks of conflict, before battlefield realities, domestic politics, and diverging national interests begin pulling partners in different directions.

To address this, the report proposes forming formal “security contracts,” or a memorandum of understanding, early in future conflicts that clearly define shared political objectives, expected end states, standards for humanitarian conduct, and mechanisms for periodically reassessing strategy.

Dr. Rand also recommends keeping consistent communication across the entire U.S. national security apparatus, warning that mixed signals from different agencies make it easier for partners to ignore American advice or exploit disagreements inside Washington.

Perhaps most notably, the report argues that future administrations should not focus solely on influencing allies. Even in conflicts involving close partners, Washington should simultaneously pursue diplomatic means with adversaries whenever possible, recognizing that negotiated settlements often require engaging both sides rather than relying exclusively on pressure directed at friendly governments.

Ultimately, the analysis shows that the challenge confronting U.S. policymakers goes beyond any single conflict. As interstate wars, civil wars, and proxy wars become increasingly protracted, America’s ability to translate military assistance into political influence may continue shrinking unless it fundamentally rethinks how partnerships are managed from the very beginning of a war.

“The United States must be brutally honest with its partners,” Dr. Rand writes. “The United States must recognize that pressuring its partners to end wars will get harder, not easier, as time passes and the partner grows better able to resist U.S. pressure.”

Study: Dr. Dafna H. Rand, Why can’t the United States end allies’ wars?, Brookings Institution Foreign Policy at Brookings (2026).

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com