Pete Hegseth, the new U.S. Secretary of Defense, is reviewing how many American soldiers are stationed in Europe and telling European allies they need to spend much more on their own militaries. This is changing how the U.S. approaches defending Europe.

Hegseth took office on January 25, 2025. Since then, he has told NATO members—the military alliance that includes the U.S. and most European countries—that Europe must treat its own defense as its most important responsibility. He says European countries should pay for "an overwhelming share" of their own defense rather than relying on American soldiers and money to protect them.

Along with his public messages, Hegseth ordered the Pentagon to examine where American troops are stationed in Europe and whether those positions still make sense for U.S. goals. When he discussed this review, he was careful to say it does not mean America is abandoning Europe. That matters because European governments have been trying to figure out if the new U.S. administration really wants to change how America helps defend Europe, or just wants to use the threat of change as leverage in negotiations.

Hegseth has also said that NATO is "the most successful defense alliance in history." But he says it will only survive if member countries do much more. He focuses on military strength—what he calls "hard power"—over the bonds of friendship and shared history that hold the alliance together. By both praising NATO and demanding it change, Hegseth is trying to push for real reforms without threatening to leave the alliance.

To understand why this matters, you need to know a bit about NATO's defense spending rules. In 2014, NATO members agreed that each country should spend 2 percent of its total economy on military defense. For years, most European countries did not meet that target. After Russia invaded Ukraine in February 2022, some countries—like Poland and the three Baltic states—started spending more. But many other European countries still spend less than 2 percent. When Hegseth demands an "overwhelming share" of defense spending from Europe, he is asking for much more than 2 percent. He is saying that Europe should lead its own military defense, not follow America's lead.

For European military planners, this creates real problems. The United States has over 80,000 troops in Europe right now—more than before Russia invaded Ukraine. These troops do more than just stand guard: they bring advanced systems for command, communication, and supplies that European armies do not have yet. They also have high-tech weapons like long-range precision missiles and intelligence-gathering systems. If the U.S. removes many of these troops, European countries would have to quickly build or buy these systems themselves—something their military budgets and timelines are not yet prepared for.

European governments have reacted differently to Hegseth's demands. Countries that already spend 2 percent or more on defense—especially Poland and the Baltic states—see his pressure as proof that their spending decisions were right. Countries that still spend less face a harder time: voters and elected officials do not want to drastically increase military budgets unless there is a clear, immediate threat. According to news reports, Hegseth does not seem willing to soften his demands to make this politically easier for those countries.

The real question is what the Pentagon's review will actually produce. The review could result in small changes—moving one group of soldiers here, rotating another group there—or in major reductions in the permanent number of American troops. Some options involve sending soldiers for temporary rotations instead of keeping them in Europe all the time. That costs less money during peacetime but sends a weaker message about America's commitment to defend Europe. Russia pays close attention to these decisions, and the choice between these approaches matters strategically.

Hegseth is pushing European NATO members to accept an idea that American leaders have mentioned for decades but rarely acted on: that American protection is not automatic or forever, but depends on European countries proving they will defend themselves. Whether the alliance can handle this kind of pressure without falling apart depends on what the Pentagon actually does with its review and how fast it acts.