Desperate to end Western support for Ukraine, Russian President Vladimir Putin is escalating his threats against NATO. Because Putin pays little heed to rhetorical warnings, the Trump administration must physically deter him.

To be sure, NATO has its flaws and needs fixes. But the defensive alliance also remains the most successful in history. And aside from its moral service of peace and freedom, NATO continues to provide vast economic benefits to America. But concern over Putin’s appetite for aggression is growing.