Russia’s botched invasion and Ukraine’s remarkable fortitude in fighting back have illustrated the diminishing power of the heavy and expensive unit of military power, its role challenged by nimbler, easier-to-use—and, crucially, cheaper—systems. Tanks, fighter jets, and warships are being pushed into obsolescence, giving way to new tools of conflict. In the process, we are seeing the very nature of combat change. In fact, we may be witnessing in Ukraine the final war of 20th-century militaries…

This wide-ranging success of cheaper, simpler systems against the ostensibly more advanced (but more expensive) equipment that is a feature of the world’s great militaries is something that has been prophesized for decades, since the advent of the Panzerfaust. If it is now a reality, that has significant implications for how armed forces the world over plan and strategize. As the counterinsurgency expert T. X. Hammes has argued, the improvement of defensive firepower has made forward movement very difficult, changing the balance of modern warfare very much against the attacker.

What the Ukraine conflict has revealed is that this shift might be even more dramatic than most have imagined, a change that for the past few decades has been obscured by the overwhelming battle-winning (if not war-winning) capabilities of the American armed forces. The U.S. has held such a marked technological, logistical, and training advantage that its large offensive forces were typically able to thwart the efforts of forces using smaller and cheaper equipment.