Iran and the United States exchanged intensified fire on Thursday in a weeklong escalation that has all but torn up last month¡¯s truce, but Iran¡¯s release of a U.S. citizen was seen as signaling a path to avert the resumption of all-out war.

For the first time since a memorandum of understanding paused fighting last month, the United States launched two big waves of air strikes in one day on Wednesday, mostly on targets near the coast in southern Iran.

Iran responded with missiles and drones fired at U.S. military bases in neighboring countries, including ?a major barrage at a recently expanded air base in Jordan.