The U.S. is facing increasing risks to its military forces and diplomatic presence in the Middle East as Iran is launching waves of missile and drone attacks across the region that are testing its ability to defend a swath of territory.
U.S. Central Command announced the death of a fourth American servicemember in the three-day-old campaign on Monday. Separately, three American F-15 jets were downed by apparent friendly fire over Kuwait on Monday, in one of the most significant losses of equipment for the U.S. in the operation.
Bases that house U.S. forces have also come under attack in Iraq, Saudi Arabia and Bahrain.
The challenge for U.S. forces is handling Iranian attacks across a huge swath of the Middle East while trying to coordinate air defense with local allies. In addition to defending tens of thousands of American troops stationed in the region, the U.S. must also defend dozens of its embassies and other government installations.
Iran’s stockpiles of short- and medium-range missiles, as well as swarms of explosive Shahed drones and electronic-warfare capabilities, pose a formidable threat to U.S. military bases in the region, said Ravi Chaudhary, a former assistant secretary of the Air Force in charge of installations.
“U.S. installations are going to be tested like never before in this particular conflict,” he said. “Our adversaries have demonstrated the intent and capability to go after our critical infrastructure to disrupt the ability of the United States to project air power.”
That challenge is mounting as Iran is widening its campaign of missile and drone strikes to include infrastructure that pumps much of the world’s oil and gas supply. An Iranian drone attack set fire to an important Saudi oil hub while Iranian strikes forced a halt to production of liquefied natural gas in Qatar, one of the world’s largest exporters.
Iranian threats have all but stopped shipping through the Strait of Hormuz, the world’s most important oil chokepoint which connects the Persian Gulf to the Indian Ocean.
Those facilities are defended by both U.S. and local air defenses that are now facing their most difficult test ever. U.S. commanders in the region oversee coalition air defenses that include local partners, but both have been overwhelmed at times by Iranian missiles and drones in recent days.
“They can reach our facilities and assets that are more fixed in the region. That could be embassy buildings. That could be anything that has an American flag on it,” said a former senior U.S. military official.
The depth of Iran’s stockpiles, which include inexpensive drones that it can produce at scale, point to one area where it could try to outlast the U.S., which is facing a shortage of munitions for its Patriot and Thaad missile defenses.
But the U.S. has other challenges in mounting its defense. Before the conflict, Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, warned the White House that a fight with Iran risks American casualties and could deplete munitions needed for future conflicts with adversaries like China.
“We have a very finite number of certain munitions,” said Daniel Byman, the director of the Warfare, Irregular Threats and Terrorism Program at the Center for Strategic and International Studies. “The other thing is, there’s, there’s a lot to defend.”
In addition to shooting missiles and drones out of the sky, the U.S. military has other measures it can take, including dispersing aircraft and other assets across a wide area so they are less vulnerable to individual attacks, a technique the U.S. used before the Iranian strike that aimed at a U.S. base in Qatar last year.
Even when incoming Iranian missiles are successfully intercepted, the blasted remains of those missiles can be lethal. Falling debris killed people in the United Arab Emirates and in Syria over the weekend.
The U.S. Embassy in Kuwait on Monday warned people not to come to the building, citing in part the risk of falling debris.
After the downing of the F-15s on Monday, the U.S. Central Command, which is responsible for the Middle East, said six crew members ejected safely after their jets were mistakenly shot down by Kuwaiti air defenses amid attacks by Iranian aircraft, ballistic missiles and drones. The crew were in stable condition, it said.
Verified video showed an American jet fighter spinning as it fell to the ground. The Wall Street Journal geolocated the video to an area on the edge of the capital, Kuwait City. A second video verified by Storyful showed people parachuting to the ground nearby. Onlookers wondered whether the parachuters were Iranian.
The incident came a day after the U.S. announced the first American deaths in the war. President Trump warned Sunday that casualties are inevitable as the U.S. military continues to strike Iran.
“And sadly, there will likely be more before it ends. That’s the way it is,” he said in a video posted on social media.
Write to Jared Malsin at jared.malsin@wsj.com and Omar Abdel-Baqui at omar.abdel-baqui@wsj.com