Overreach, then, is the more immediate threat. No one expected the array of sanctions, designations, technology controls and asset freezes to be assembled as quickly, or at such scale. Now there is a nearly palpable air of giddiness among policymakers. Every day brings new restrictions that build on one another. European officials have mused that they might use this new form of economic warfare to “bring down” Mr. Putin’s regime or “provoke the collapse” of the Russian economy.

These statements were hastily clarified, but they illustrate a deeper danger. As a new book by the historian Nicholas Mulder emphasizes, the “economic weapon” of sanctions and blockades doesn’t work nearly as predictably or effectively as its proponents imagine. The more powerful sanctions are, the greater the danger that they will lead to an unpredictable response. As Mr. Mulder demonstrates, fears of sanctions helped propel Nazi Germany’s territorial ambitions. More recently, when Iran was feeling badly squeezed by sanctions, it was accused of attacking shipping through the Straits of Hormuz, a key chokepoint in the global energy economy. The closer Mr. Putin’s regime comes to collapse, the more likely that it will lash out.

This doesn’t mean that the United States and its allies should stop using their control of global economic networks as a weapon. This is one of the few means they can responsibly use against a nuclear power in an unprovoked war.