Authorizing foreign wars is the job of U.S. lawmakers, but recent presidents have stretched their own powers to engage in global conflicts.

The prospect of a U.S. strike against Iran has exposed divisions in the coalition of supporters that brought President Donald Trump to power, with some of his base urging him not to get the country involved in a new Middle East war.

President Trump’s political base is splintering over the prospect that the U.S. could join Israel’s assault on Iran—and the White House is trying to quell the backlash.