On Sunday, President Trump declined to join Saudi Arabia in joint military strikes against the Houthis in Yemen, choosing restraint over deeper regional entanglement — at least for now. The decision carries weight beyond Yemen itself, as Trump simultaneously pursues a confrontational strategy toward Iran that depends heavily on Saudi cooperation and goodwill. In the long arc of great-power alliance-making, this is the familiar tension of asking an ally to follow your lead while declining to follow theirs — a negotiation that rarely stays quiet for long.