Surveying the maritime security setting reveals some glaring anomalies. To name one: Europeans fret constantly about Russian mischief-making at their door, yet they constantly build down the military and naval forces needed to deter or defeat aggression. Great Britain’s Royal Navy is now smaller than the French Navy for the first time since the day of Nelson and Napoleon, and appears poised to disband its amphibious fleet. The NATO secretary general boasts that (barely) over half of Alliance members will meet the exceedingly humble minimum standard of spending 2 percent of GDP on defense. They will do so by . . . 2024.

That underwhelms. It also defies predictions that grave threats draw forth serious replies from those threatened. One doubts President Putin spends much time cowering before the European juggernaut.

Scrimping on self-defense is not a new phenomenon on the Continent. Back in 2002 analyst Robert Kagan published a small book that always struck me as having a large truth quotient. In Of Power and Paradise Kagan contends, in brief, that Americans are from Mars while Europeans are from Venus. Having provided for military security in what Nicholas Spykman called the “rimlands” of Western Europe and East Asia for many decades, Americans see force as a natural implement of statecraft. Having sheltered underneath U.S.-furnished security for all those decades, Europeans have come to believe military defense is something others do.

The enlightened trust to peaceful negotiations and international law and institutions—and, from time to time, rebuke their defenders for their retrograde ways.

Kagan probably overstated his brief for power and paradise, but there is a reason it stung on the Continent. Americans shouldn’t gloat too much, though; there was a time in our history when we indulged the same fantasy, and when we were the beneficiary of European-supplied security. Except for a brief surge during the Civil War, the U.S. Navy remained an afterthought until the 1880s, when Congress authorized the Republic’s first modern battle fleet. For most of the Monroe Doctrine era, in other words, the United States had little way to uphold James Monroe’s grandiose pronouncement barring new European colonies in the New World.

But it was enforced. Erstwhile foe Great Britain was a silent partner in the Monroe Doctrine, and its Royal Navy provided the muscle. Britain had interests of its own in keeping rival empires out of the Americas. Americans took that invisible protection for granted—and neglected to provide for their own defense heading into the twentieth century. Back then Britons were from Mars and Americans were from Venus.

Britain ultimately withdrew from the Western Hemisphere to confront a rising Imperial Germany. It had to put its interests first, as all nations do. A lesson for Europeans from a century ago: your protector protects you to advance its own interests. If its interests dictate that it concentrate resources elsewhere, you could find yourselves in a very bad place.

Best to start doing more now.