Recently, the Trump administration reportedly told its allies it would stop participating in military exercises in Europe, including those already scheduled for 2025.

I served as deputy assistant secretary of Defense for Force Education and Training in the Biden administration, where I had policy oversight of military exercises. I can say with confidence that the decision to pull out of European exercises is a severe strategic mistake. There are three reasons why.

First, exercises with allies are the mortar in the foundation of U.S. defense strategy: they keep the whole thing together. This is because the United States military doesn’t fight alone. It never has, and, barring a tectonic shift in U.S. strategic and operational concepts, likely never will. Therefore, anything that erodes the ability of the United States and its allies to fight together threatens the viability of U.S. military power.

Exercises are the best mechanism available to forge interoperability and validate that U.S. and allied forces are ready for the fight. Readiness is about more than weaponry — it’s the cognitive interoperability of the personnel using the weapons that makes the difference. Only repeated engagements synthesizing the smallest tactical challenges (like how to make two different radios talk to each other) with the biggest strategic goals (how to ensure multiple armies can secure territory and deter an adversary) can create the kind of lethal combat readiness Americans expect and the world envies.

Second, the only currency that buys that interoperability is time, which the logistical chaos created by pulling out of exercises wastes needlessly. Because of their complexity, even simple exercises can take at least a year to plan.

© The Hill