The United States’ security ties with Europe are fraying. Even before the war in Iran returned the Middle East to the front of policymakers’ minds, the United States was already shifting its focus away from Europe and toward deterring China in the Indo-Pacific. The move is occurring at a perilous moment, with Russia pressuring the continent from its eastern flank as it fights to subjugate Ukraine. As a result, Europeans feel increasingly compelled to take care of their own defense.

Donald Trump’s return to the presidency has accelerated this process. He has criticized European countries for insufficient contributions to collective defense and threatened to reduce the number of U.S. forces available to NATO during crises. But the truth is that the underlying shift in transatlantic relations is structural, not personal. Even if future administrations are less hostile to NATO, the United States is unlikely to reverse its broader shift away from Europe. As a result, discussions over rearmament and defense integration have become a hot topic across the continent’s capitals.

European leaders continue to disagree over how fast they can move and how much they can accomplish. But with sufficient spending, planning, and will, the continent should be able to assemble enough troops and conventional weapons and dramatically reduce (if not totally eliminate) the need for large-scale U.S. ground forces in Europe within a decade. And because both France and the United Kingdom have nuclear arsenals, deepening cooperation with London and Paris could also strengthen Europe’s nuclear deterrence.

But building these military capabilities is one thing; effectively using them is another. And no matter how well Europe rearms, it cannot adequately reproduce the United States’ military enablers—the systems that make up the backbone of modern warfare. Washington possesses unparalleled capacities across a variety of capabilities, including command and control; logistics; training; cyberwarfare and cyberdefense; long-term strategic intelligence; battlefield intelligence, surveillance, and reconnaissance (collectively known as ISR); targeting; and air and missile defense. It has built up these systems over decades, and Europe has long been able to rely on them. Effectively reproducing them would take at least a decade of lead time and a level of funding that is likely beyond the continent’s means.

Europe thus needs a plan to secure reliable access to this suite of military enablers for the foreseeable future. It should propose a new transatlantic bargain that creates durable financial and strategic incentives for the United States to continue providing these critical military capabilities. Doing so would help reduce the risk that an increasingly disengaged Washington abruptly curtails some or all enabling support—and inject a measure of stability into the alliance in this era of strategic upheaval.

Washington has spent generations—and trillions of dollars—accumulating specialized capabilities that allow its military to operate at an enormous scale while minimizing casualties through precision, coordination, and information dominance. It has, for example, developed an unparalleled capacity to instantaneously gather battlefield information via a massive network of satellites and air, ground, and sea sensors, communicate it via complex encrypted networks, and process and act upon it in real time via personnel and institutional structures whose expertise has been honed over decades. These enablers have made the American way of war, and by extension the NATO way of war, possible. They have been indispensable for Washington’s allies and........

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