By Eric Vandenbroeck and co-workers

America’s Quasi Alliances: How Washington Should Manage Its Most Complicated Relationships

During his successful 2024 U.S. presidential campaign, Donald Trump assured voters that he would end the wars in Ukraine and Gaza, perhaps even before taking office. But both conflicts dragged on at great human cost, and diplomacy proceeded only in fits and starts. Nine months into his presidency, Trump finally brokered a cease-fire between Israel and Hamas—but only after presiding over the breakdown of the truce he inherited from President Joe Biden and an escalating humanitarian crisis in Gaza. The war in Ukraine, meanwhile, continues unabated.

These challenges are not unique to Trump; they bedeviled Biden, too. Indeed, the difficulty of bringing both wars to an end illustrates the strategic dilemmas facing the United States in managing a small but critical subset of its partners: so-called quasi allies. Quasi allies—which, since the end of World War II, the United States has cultivated as it has built its alliance system—are more than partners but less than treaty allies. They have special status in Washington, but they lack the feature of an alliance that matters most: a formal U.S. security guarantee.

The recent wars in Ukraine and the Middle East have put quasi-allies at the center of U.S. foreign policy. The United States has supported Ukraine in resisting Russia’s attempt at subjugation, sending billions of dollars’ worth of advanced weaponry to its armed forces. Ukraine has maintained its sovereignty and political independence, whereas Russia has suffered more than a million military casualties and significant materiel losses—results achieved without direct conflict between Moscow and Washington. In the Middle East, the United States has enabled an Israeli-led campaign that set back Iran’s nuclear program and broke its regional network of armed proxy groups, even as those operations also deepened the humanitarian catastrophe in Gaza. This record points to the advantages of supporting strong quasi-allies at the frontlines of geopolitics: these relationships allow the United States to advance its interests in consequential regions through indirect, less costly means.

But the United States’ attempts to manage its role in these wars have also highlighted strategic dilemmas endemic to quasi-alliances and particularly pronounced in wartime. If Trump is to fulfill his goal of bringing peace to the Middle East and Europe, his administration needs to better manage these dilemmas. And Washington’s experience with Ukraine and Israel should inform planning for a high-stakes contingency involving Taiwan, another quasi-ally in a perilous neighborhood.

U.S. President Donald Trump meeting with Ukrainian President Volodymyr Zelensky in Washington, D.C., October 2025

 

More Than Friends

Within its vast network of relationships around the globe, the United States categorizes most of its friends as either allies or partners. Washington is bound to its allies by legally codified treaties featuring mutual defense clauses. This pledge that an attack on one is an attack on all backstops allies’ security and extends the U.S. nuclear umbrella. Partners, by contrast, may receive security assistance from the United States but do not presume that the U.S. military would come to their aid if they were attacked.

Quasi allies represent an awkward third category. These are countries through which the United States sees opportunities to advance its interests. They may receive significant military training and assistance, host a large U.S. troop presence, and coordinate closely with Washington. Some even enjoy a confusing designation, conferred by the president, as a “major non-NATO ally,” which does not entail a security commitment. Unlike partners, the scope and scale of Washington’s investment in their security creates ambiguity around whether and to what extent the United States would intervene to defend quasi-allies if they were attacked. Indeed, the United States has occasionally come to the defense of its quasi-allies, as when it helped Israel defeat Iranian aerial attacks twice in 2024 and again during the Iran-Israel war in June. But there tend to be good reasons why the United States stops short of extending the kind of mutual defense commitment that would cement a treaty alliance—including concerns about becoming entangled in a turbulent region, provoking an adversary, or pledging to defend a partner that may not pursue Washington’s preferred policies. This ambiguity makes quasi-alliances weaker tools of deterrence and reassurance than formal alliances, and it helps explain why quasi-allies are more vulnerable to external aggression than treaty allies.

Despite Washington’s deep investment in these relationships, quasi-allies often have interests that diverge from those of the United States. Quasi-ally leaders have their own agendas and domestic politics, especially when their country is at war. The United States has repeatedly experienced these dynamics with Ukraine and Israel, a challenge I witnessed firsthand as a senior official in the Biden White House. In both cases, U.S. policy sought to enable quasi-allies to pursue common objectives while managing disagreements over diplomatic and military strategy.

During Ukraine’s 2022 counteroffensive campaign against Russia, Ukrainian and U.S. military leaders jointly developed a strategy to punch through Russian defensive lines in Kherson and take territory that would enable Ukrainian forces to break the land bridge connecting Crimea with occupied Ukraine. Yet this plan foundered when confronted with Ukraine’s understandable loss aversion—breaching Russian defenses would have been an exceptionally bloody endeavor—and distracting rivalries among Ukrainian commanders and political leadership. Despite careful joint planning, U.S. policymakers could do little to compel Ukraine to see the campaign through. Domestic political imperatives have similarly prevented Ukrainian President Volodymyr Zelensky from taking the painful but necessary step of lowering the draft age from 25 to 18 to address manpower shortages, which in turn has exacerbated demand for military materiel from the United States and Europe.

The dilemma of divergent interests has also challenged U.S. policymaking toward Israel since October 7, 2023. Hamas’s heinous attack came at a moment when Israeli Prime Minister Benjamin Netanyahu was politically vulnerable and facing serious corruption charges. He has deftly managed to stay in power, often by taking steps opposed by Washington: restricting humanitarian aid into Gaza, expanding West Bank settlements, and escalating attacks on Iran and Hezbollah, its Lebanese proxy militia. The past two years have thus exposed real policy differences, as well as the limits of U.S. influence over Israeli decision-making.

 

Skin in the Game

The United States may also diverge from its quasi-allies on how to assess or manage the risk of escalation. Although Washington may have a strong strategic interest in the outcome of wars involving quasi-allies, it can choose to calibrate its involvement. For the quasi ally, the stakes are always higher and often existential. They may be more willing to gamble on steps that could lead to significant escalation, including actions that could draw their sponsors into direct conflict. And in some cases, entanglement is the point.

Kyiv’s greater risk tolerance has created friction in the U.S.-Ukrainian relationship from the early months of Russia’s invasion. During the Biden administration, Ukrainian leaders had a perennial wish list of ever more capable weapons systems. Long-range missiles known as ATACMS (Army Tactical Missile System) topped the list, and unlike some other sophisticated systems the Ukrainians requested, these promised real military utility. But Biden officials believed that providing these missiles carried risks in terms of U.S. military readiness and the potential for escalation. The subsequent years-long push and pull between Kyiv and Washington distracted from other policy debates and Ukrainian military imperatives. By the time Biden authorized the shipment of a limited number of ATACMS to Ukraine in April 2024, with clear restrictions on their use, the weapons provided tactical benefits but did not generate a strategic breakthrough. A similar dynamic played out, albeit less publicly, as Ukraine repeatedly sought permission to use U.S. equipment to strike Russian territory. Ukraine ultimately won the United States’ limited acquiescence.

In both cases, Ukraine was willing to gamble to score military or even morale-boosting wins and would likely have welcomed direct U.S. military intervention, whereas Washington sought to both meet Kyiv’s military needs and avoid the kind of escalation that would draw the United States or NATO directly into the war. Attempts to resolve this tension resulted in suboptimal policies for both sides: Washington accepted more risk than it wanted to, but not enough to deliver Ukraine a decisive boost.

The United States has managed similar tensions with Israel in its recent wars with Hezbollah and Iran. In the days immediately following October 7, Biden dissuaded Israel’s leadership from launching a preemptive strike on Hezbollah and parried Netanyahu’s request for U.S. military participation in the strike by arguing that it would trigger a regional firestorm at a time when Israel was ill-prepared for a multifront war. In April 2024, after Iran launched its first aerial attack on Israel, Biden told Netanyahu that the United States would not support an Israeli counterattack against Iran, urging him to take the unsuccessful nature of the Iranian salvo as a win, thanks to joint defensive operations. Netanyahu partially accepted this advice, hitting a strategic air defense site inside Iran without claiming public credit for the strike.

When Trump took office, he clearly signaled a strong preference to address Iran’s nuclear program via diplomatic means. Israel nevertheless launched a military campaign against Iran. The fact that only the U.S. military had bombs capable of penetrating Iran’s nuclear facilities meant that Netanyahu was betting on Washington’s ultimate involvement, a gamble that paid off in June, when Trump authorized U.S. strikes. Of all the points on which interests diverge between the United States and its quasi-allies, escalation and risk tolerance are the highest-stakes areas because the danger of entanglement is the greatest.

 

The Limits of Leverage

If relative power and material dependence translated neatly into influence, the United States would have overwhelming leverage over its quasi-allies, resulting in an ability to manage tension through coercive means, such as withholding weapons, and to dictate wartime decisions. But the reality is more complicated. The relationship between the United States and its quasi-ally is itself a center of gravity, especially during wartime: if the relationship frays, the break advantages the adversary.

When quasi-allies fight enduring wars, the most effective way for the United States to secure its desired outcome is either to help its partner win the war outright or to convince the adversary that support will continue to flow until a favorable negotiated settlement is reached. These dynamics make it difficult to withhold vital military support as leverage in shaping how a quasi-ally fights and what peace it will accept. And it makes wars involving support to quasi-allies challenging to end.

In his bid to end the war in Ukraine, Trump calculated that Ukraine’s dependence on the United States meant that he could browbeat Kyiv into a negotiated settlement that heavily favored Moscow. Trump tested this hypothesis by publicly berating Zelensky in the Oval Office, then cutting off military and intelligence assistance. Rather than coercing Ukraine into war-ending concessions, however, this gambit only spotlighted the frailty of the bonds between Kyiv and Washington under the Trump administration and led the Kremlin to double down on its strategy of diplomatic recalcitrance and intensified military pressure.

Biden took the opposite approach. In 2022, the United States and its G-7 allies declared their intent to support Ukraine for “as long as it takes.” This commitment and the consistent support that followed bolstered Ukraine’s will to fight and telegraphed that time was not on Russia’s side. But it obscured two difficult realities: that Congress would not indefinitely sustain billions of dollars in support to Ukraine and that ending the war would inevitably require pressuring Kyiv to step back from its unattainable near-term objective to restore its pre-invasion border.

The United States’ efforts to use its leverage to moderate Israel’s maximalist war aims and to end the war in Gaza were always fraught and only grew more so as the humanitarian calamity in Gaza deepened. The Biden administration continually wrestled with the question of whether and how to condition military support to Israel at a time when Israel remained under threat from Iran and Hezbollah. It came closest to doing so in May 2024, in anticipation of major Israeli military operations in Rafah. Concerned that this move would endanger nearly a million civilians and undermine prospects for a cease-fire, Biden proclaimed he would not supply the weapons for the offensive and paused the delivery of 2,000-pound bombs. Biden officials ultimately succeeded in persuading Israel to downscale its Rafah operation, one of several modest successes in using pressure to improve humanitarian outcomes in Gaza, and never resumed the delivery of 2,000-pound bombs. But the administration’s concern about limiting support to Israel while it faced other regional threats constrained the options for further restrictions.

Trump has taken a very different approach. During his first nine months in office, he largely gave Israel free rein to conduct its Gaza operations as it wished, effectively backing its decision to restart the war in March after a cease-fire, stop humanitarian aid deliveries, and push into Gaza City. But after Israel attempted to kill Hamas negotiators with a September airstrike in Qatar, Trump changed tack and pressured Netanyahu to agree to a cease-fire. With a credible, if seemingly nonspecific, threat of abandonment, Trump compelled Netanyahu to accept elements of a peace plan he had previously opposed and pause the war. Although the United States’ relationship with Israel is the most politically charged, the United States will always face tradeoffs between the strategic benefits of fulsome support to quasi allies and the temptation to parlay that support into meaningful influence over military and diplomatic decision-making.

 

Threading the Needle

The strategic dilemmas that quasi-alliances pose are endlessly frustrating to policymakers. But they are here to stay. Ending the war in Ukraine on favorable terms and preserving a fragile truce in Gaza will require deft navigation of these dilemmas. Several lessons emerge from the United States’ recent experience with Ukraine and Israel. First, leaders face a temptation to paper over differences and exaggerate the convergence of interests, especially when helping to defend a close partner against brutal aggression. But Washington should commit to supporting quasi-allies in wars only if they have clearly defined objectives that closely correspond with its own. Once the United States decides to undertake such support, it should build mechanisms to align priorities and privately manage disagreements. Models include U.S.-Ukrainian military planning channels and the national security adviser–led U.S.-Israeli strategic dialogue on Iran. And clear leader-level communication is paramount.

Policymakers should also design credible forms of leverage to shape quasi allies’ behavior. Security assistance should be strategically calibrated—a reframing that emphasizes U.S. interests rather than the coercive connotations of aid conditionality. Such a process begins with conveying clear expectations in writing, such as end-use restrictions on U.S. military equipment. Even minor violations should be addressed early to create an expectation of enforcement. If the White House keeps up a regular cadence of reviews of U.S. arms deliveries, it can better ensure that the pace and content of these transfers are aligned with policy objectives and legal requirements, not conducted on autopilot. Congress is an essential partner: it can legislate restrictions itself as well as help preserve leader-level relationships by deferring blame to Capitol Hill.

Careful public messaging can make all of this easier. It is crucial to project strong support for quasi-allies and explain that support to the American public without creating commitments that become politically costly to walk back. Too often, critics of Biden’s sound Ukraine policy seized on the difference between his soaring rhetoric and his well-founded escalation concerns. Adhering to a policy that there should be “no daylight” between the United States and its quasi-ally is a mistake because it creates an impossible choice between burying disagreement and absorbing the political blowback associated with a public break.

An even more consequential conflict involving a quasi-ally could be lurking on the horizon: war between China and Taiwan. The United States could quickly become a direct combatant in such a conflict, assuming far more risk but also exerting much greater influence over the course of the war and its outcome. But even if the United States intervenes outright on Taiwan’s behalf, quasi-alliance dilemmas would resurface: divergent interests and domestic-political incentives, especially given Taiwan’s highly polarized politics; escalatory steps by Taipei that could undercut Washington’s efforts to carefully manage risk; and the difficulty of finding a mutually acceptable endgame. These challenges all place a premium on quiet peacetime coordination between Washington and Taipei to build alignment on notional military plans and war aims, procedures for escalation management and signaling to Beijing, and conditions for terminating a war.

Leaders cannot wish away close friends such as Israel, Taiwan, and Ukraine that straddle combustible geopolitical fault lines—nor would it benefit the United States to do so. But to advance U.S. interests, Washington needs better answers to the strategic dilemmas inherent in managing quasi-alliances. Only by grappling with recent successes and failures can policymakers develop a better playbook.

 

 

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