The vast majority of deaths reported so far have been in Iran, but the human toll is being felt around the world.
Shipping companies are not sending oil and gas through the Strait of Hormuz because they fear their ships might be attacked.
The Pentagon and Middle Eastern countries say that most of the drones have been intercepted. But some have slipped through and caused damage.
The wars in Afghanistan and Iraq offered a stark lesson in the limits of military force. The Iran attacks suggest an era of postwar wariness is over.
Much of Tehran’s arsenal of missiles may be hidden underground, making it harder to destroy.
President Trump also declined to rule out sending ground troops into Iran as the conflict spread into the Gulf countries and Lebanon and Israel exchanged strikes.
The secretary of state signaled that an escalation in Iran was likely and said the attacks underway were both pre-emptive and defensive, describing a far more extensive mission than was initially laid out.
The number of U.S. service members killed in the first three days of the war grew as officials said the remains of two more troops had been recovered.
President Trump’s embrace of military action in Iran was spurred by an Israeli leader determined to end diplomatic negotiations. Few of the president’s advisers voiced opposition.
Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, acknowledged the possibility of an extended campaign, as the military announced that six U.S. service members had been killed so far.