A weekend of official explanations for President Trump’s airstrikes on a Syrian air base has only deepened the confusion over his intentions, next steps and the legal basis for his unilateral use of force in the middle of that complicated, intractable civil war. The administration will have to do better than this.

Presidents have an obligation to explain military operations to the American people and the world, and, when possible, most begin making their argument well before they take action. In Mr. Trump’s case, the need for clarity is even greater given that the attack on Thursday, in retaliation for President Bashar al-Assad’s use of chemical weapons on civilians, was a reversal of the position he campaigned on just months ago.

Now that Mr. Trump has ordered a strike against the Assad government, how far is he prepared to go to end the six-year-old civil war? What does the operation say about his willingness to use force beyond Syria? One troublesome answer may be found in Secretary of State Rex Tillerson’s comments on Monday. “We rededicate ourselves to holding to account any and all who commit crimes against the innocents anywhere in the world,” he said on a trip to a World War II memorial in Italy, a trip aimed at rallying allies and Russia around a strategy to end the Syrian war.