This is part five of a series examining the challenges confronting the .
For more than three decades, the U.S. carried the largest share of NATO’s military burden while many European allies spent far less on defense than Washington wanted.
The imbalance survived the Cold War, multiple U.S. administrations and repeated debates over burden sharing. Only in recent years â following Russia’s 2022 invasion of Ukraine and renewed pressure from President â have many NATO members begun significantly increasing defense spending.
So why did the gap persist for so long?
Defense analysts say the answer lies in a combination of post-Cold War optimism, domestic political priorities and an American defense umbrella that convinced much of Europe it could safely spend less on defense without sacrificing its security.
“For much of the postâCold War period, it is fair to say that Europeans underinvested in defense, partly because threats were low, and partly because a series of U.S. presidents did everything they could to convince Europeans that we would stay there forever,” Barry Posen, a professor of political science at the Massachusetts Institute of Technology, told Fox News Digital.
The collapse of the Soviet Union reinforced that mindset.Â
With the primary threat NATO had been created to deter suddenly gone, governments across Europe moved to collect a so-called “peace dividend,” redirecting resources toward domestic priorities and away from their militaries.
Between 1992 and 1999, defense spending among European NATO members fell 22%, helping establish a pattern of underinvestment that would persist for decades even as the United States maintained and continued serving as NATO’s ultimate security backstop.
As defense spending declined, many European governments expanded or maintained social welfare systems that consumed a growing share of public budgets. Programs such as healthcare, pensions and higher education became deeply embedded in domestic politics, often making them harder to cut than military spending.
With the U.S. continuing to provide the bulk of NATO’s military power, many governments faced little immediate pressure to reverse course. Critics of the alliance’s spending imbalance argued that American taxpayers were effectively subsidizing Europe’s security, allowing allies to devote a larger share of public resources to domestic priorities.
The result was what some defense analysts describe as a “moral hazard” problem: because the U.S. commitment to NATO was viewed as ironclad, allies could spend less on their own militaries without facing the full consequences of those decisions.
Over time, that dynamic became self-reinforcing. As European militaries shrank, many allies grew increasingly dependent on American capabilities ranging from logistics and intelligence to missile defense, strategic airlift and nuclear deterrence.
“We are still having a strong, conventional U.S. presence in Europe,” NATO Secretary-General Mark Rutte said earlier in 2026, “and, of course, the nuclear umbrella as our ultimate guarantor.”
American frustration over burden sharing is nearly as old as NATO itself.
In 1953, President Dwight D. Eisenhower warned European allies that “the American well can run dry” and pressed them to assume a larger share of the alliance’s defense burden. The issue resurfaced repeatedly over the following decades as successive administrations sought greater European contributions to collective defense.
The concern persisted long after the Cold War. In a blunt 2011 farewell speech in Brussels, then-War Secretary Robert Gates warned of a “dim if not dismal future” for NATO if European governments continued underinvesting in their militaries. Gates cautioned that there would be “dwindling appetite and patience” among American lawmakers and taxpayers to bear a disproportionate share of the alliance’s defense costs.</p
