Yet, exactly how and why the Trump administration decided to go to war with Iran remains murky. Unlike in 2002, when President George W. Bush’s administration made its case to Congress and the world for its invasion of Iraq, Mr. Trump did little to prepare Americans ahead of time for military action. He has offered various reasons for ordering airstrikes, and both called for a popular uprising in Iran and said he wanted to deal with a more “friendly” regime. His officials have said the military objective is to destroy Iran’s missile stockpiles and its offensive capabilities.