Intelligence assessments suggest Iran used the eight-week ceasefire to replenish its arsenal, potentially integrating Russian weapons to restore combat capabilities.

Western allies believe Iran has most likely added new-build Russian weapons to its inventory and reconstituted large swathes of its missile arsenal during the eight-week ceasefire, giving the Islamic Republic the firepower to strike back at nearly full strength if hostilities resume. Tehran has about three-quarters of the munitions it had before the war and can easily build it up further, according to intelligence assessments. That includes unspecified Russian missiles that probably came off the...