Three days after coordinated terror attacks in Paris killed at least 129 people and put the lie to President Obama’s recent claim that Islamic State was “contained,” Mr. Obama took to the podium on Monday. Speaking from Antalya, Turkey, where he was attending a G-20 meeting, he threw the full weight of his rhetoric behind solidarity with France and behind the French military response against Islamic State, or ISIS. But he offered no policy changes. In other words, once again America is leading from behind.

Mr. Obama’s remarks...