The Iranian attack that killed two U.S. soldiers and left one service member missing on Friday was the fourth in five days on U.S. forces in Jordan, multiple American officials said. Taken together, the attacks have wounded dozens of U.S. service members and damaged a number of helicopters.

The flurry of attacks and the losses they have caused are a sign that Iranian forces not only still have ample missile stocks but have also become more adept at evading U.S. air defense systems, said the U.S. officials, who were speaking on condition of anonymity to discuss operational matters.

Jordan, which hosts major U.S. air bases, grew in importance in the run-up to and the early days of the war, as the Pentagon shifted a number of troops from Bahrain, the United Arab Emirates and Qatar to relatively more secure locations in Jordan and Israel. The country’s role in U.S. operations has only increased as other American allies in the region have restricted Washington’s ability to base troops in and fly aircraft over their territories, the U.S. officials said.

In early July, Iran widened its attacks in the region, including Jordan for the first time since Tehran and Washington signed a cease-fire agreement in June.

The U.S. officials offered a recounting of the last five days of Iran’s attacks on Jordan, which the Pentagon has not yet discussed in detail publicly.

The first attack to hit U.S. forces in Jordan struck a residential facility at King Faisal Air Base, wounding as many as five U.S. service members, they said. The second hit a base in eastern Jordan where U.S. Blackhawk helicopters were operating from, damaging a significant number of them.

Then, 48 hours ago, Iranian missiles hit Jordan’s Muwawffaq Salti Air Base in Azraq, which is the same base where the troops were killed on Friday, the officials said. The earlier strike wounded about 20 U.S. troops rushing to take cover in bunkers. No one was killed in that barrage. But on Friday, when the Iranians struck the base again, two U.S. troops were killed and four other service members were injured, according to U.S. officials. Other personnel were evaluated for minor injuries and returned to duty.

The Pentagon did not immediately respond to a request for comment on these events.

On Friday, the Iranian Army said it had launched a drone attack targeting fuel tanks at the U.S. base in Azraq. The Islamic Revolutionary Guards Corps also said it had used missiles and drones to target aircraft shelters at the base, according to Fars News Agency, a semiofficial news outlet affiliated with the Guards.

President Trump has signaled that he plans to increase strikes on Iran in the next week and intended to hit more Iranian infrastructure, including bridges, electrical power plants and distribution systems. The deaths of the U.S. soldiers in Jordan increase the likelihood that Mr. Trump, who has threatened such strikes in the past but sometimes pulled back, will follow through.

Eric Schmitt contributed reporting.