What’s in doubt is whether growing common cause among European leaders and significant increases in European defense spending can unfold quickly enough to save Ukraine without significant help from the U.S. It also remains to be seen if these factors can restore deterrence in the Euro-Atlantic area to discourage a Russian threat materializing before 2030.

These days, deterrence must also account for the so-called “grey zone.” Russia is already eroding NATO’s Article 5 commitment to mutual defense through attacks that fall into this hybrid category, all designed to weaken resolve without triggering a conventional military response. And it is likely to escalate such calibrated provocations including, for example, undersea cable sabotage, cyberattacks on power grids or missile “accidents” near NATO territory. All this is a deliberate strategy to expand Moscow’s influence.

Meanwhile, on the battlefield in Ukraine, we’re seeing a mix of World War I and World War III — a real-time case study foreshadowing some aspects of future warfare. Over the last few years, we have witnessed how fast the character of conflict evolves, and how the boundaries between land, sea, air, space and cyberspace fade as we seek to integrate these domains for advantage.

Here, many rightly point to Ukraine’s ingenuity in adapting under fire, but Russia has innovated at equal speed and scale: deploying cheap drones, electromagnetic jamming, AI-enabled targeting and retooling its economy into an engine of war. This year alone, the country will produce 1,500 tanks, 3,000 armored vehicles and 200 ballistic missiles — matching NATO’s annual output in a matter of months.

Given this pace of technological change, keeping abreast of innovation is critical, and Europe’s defense planning must be built on that principle. In warfare, the side that adapts fastest has always had the best chance of winning — not least, as military historian Sir Michael Howard observed: “Everybody gets it wrong so the important thing to do is to develop the intellectual capacity to adjust faster than the other guy.”

But Europe needs a fundamental rethink — not only of the capabilities required both now and in the future, but of how its systems and institutions must change to deliver them. This means scaling up defense production, modernizing forces, rethinking procurement and investing in the right mix of capabilities for today’s threats, as well as those on the horizon.