Biden’s Kyiv visit shows Putin seriously misjudged his courage

As President Biden walked the streets of Kyiv on Monday beside Ukrainian President Volodymyr Zelensky, air raid sirens began to wail. A Russian fighter jet had reportedly taken off from Belarus, carrying the type of hypersonic missile that Ukraine’s defenders cannot shoot down. The two leaders did not flinch.

Say what you want about Biden, he lacks neither courage nor resolve. His surprise visit to the Ukrainian capital might be the first time a sitting president has braved an active war zone — with no inviolable U.S. military cordon around him — since 1864,...