Amid Trump's Blockade, Threat of Escalation Leaves Thousands of U.S. Forces on High Alert

Thousands of U.S. troops in the Middle East are once again on high alert as a U.S. military blockade of the Strait of Hormuz that began Monday raises the specter of a new round of combat in the war against Iran.

President Trump ordered the U.S. Navy to block Iranian shipping through the narrow chokepoint after talks between U.S. and Iranian officials in Islamabad failed to land on a deal to end the war. For weeks, the Iranian military had effectively controlled the critical strait, blocking much of the traffic through the 21-mile-wide passage and disrupting the global economy.

The standoff has further undermined a shaky ceasefire that is scheduled to lapse on April 21 if the two countries don’t come to an agreement. Trump has declined to rule out deploying ground troops into Iran. 

The array of troops in the region cover a wide range of specialties and backgrounds. In March, President Trump sent the 31st Marine Expeditionary Unit (MEU) to the region on board the USS Tripoli, an amphibious assault ship floating in the Arabian Sea south of the strait. Not far away is the firepower of the Abraham Lincoln Carrier Strike Group—which includes F-18 strike fighter squadrons the “Tophatters,” the “Black Aces,” and the “Vigilantes,” and the Marine F-35 fighter attack squadron known as the “Black Knights.” The U.S. Navy has also arrayed eight Aegis guided missile destroyers in the Arabian Sea within striking distance of Iran. And Trump has ordered the 82nd Airborne elite paratroopers to deploy to an undisclosed forward base in the Middle East.  

All of those forces remain in place, giving Trump options for additional actions if the ceasefire fails, a former U.S. special operations soldier who has close ties to Trump’s Pentagon tells TIME. 

“Let us be clear: a ceasefire is a pause, and the joint force remains ready, if ordered or called upon, to resume combat operations with the same speed and precision,” Dan Caine, Chairman of the Joint Chiefs of Staff, told reporters at the Pentagon on April 8. 

Trump and others in the Administration have discussed the prospects of an attack on Iran’s principal oil depot at Kharg Island or a ground operation to seize parts of the strait’s coastline inside Iran. Trump also requested an audacious, if unlikely, military plan for an aerial assault deep inside Iran to dig up enriched uranium buried under rubble by previous U.S. strikes, and then fly the uranium out of the country.   

The 82nd Airborne and the Marines could be used to seize small areas inside Iran, experts tell TIME, but would not be able to hold territory for long on their own, especially against Iran’s arsenal of cheap, short-range, low-flying Iranian drones. Those drones, also known as unmanned aircraft systems (UAS), have proven able to slip past expensive and sophisticated American anti-missile systems.

“I wouldn't want to hold anything in the region until we fix our counter-UAS interceptor problem,” says retired Navy Rear Admiral Mark Montgomery, a fellow at Foundation for Defense of Democracies. 

For now, the blockade is primarily being enforced by the U.S. Fifth Fleet, which is based on the western edge of the Persian Gulf at a U.S. naval base in Manama, Bahrain’s capital. For decades, the Fifth Fleet has been the U.S.’s principle bludgeon to ensure freedom of navigation through the strait. But now, Trump has given the fleet the opposite mission—to block Iranian shipments instead of ensuring safe passage for all vessels.

So far, 15 service members have died in combat during the Iran War, beginning with a drone attack against a U.S. logistics port in Kuwait on March 1 that killed six American troops. Another American service member was killed in Saudi Arabia on March 8, and six crew died in a crash of an air refueling plane in Iraq on March 12.

“If the United States did renege on the ceasefire and start using either the 82nd or the MEU for purpose—that would just open up further escalation,” says Brandan Buck, a former intelligence officer with the National Geospatial-Intelligence Agency who is now a foreign policy expert at the Cato Institute. Iranian military capabilities, he adds, “are good enough to make things hurt.”

Here’s a look at the forces the U.S. has in the region that could be deployed if the fighting starts up again.

US Navy's Fifth Fleet

The U.S. Fifth Fleet is based in Naval Support Activity Bahrain, a naval base in Manama, Bahrain that hosts around 8,000 personnel. It is responsible for protecting maritime traffic in the Persian Gulf and Strait of Hormuz, and is currently enforcing a blockade of the strait. 

Iran understands the central role the base plays in the conflict. When the U.S. and Israeli attacks on Iran began on February 28, Iran targeted the base with missiles and drone attacks. 

31st Marine Expeditionary Unit

Based in Okinawa, the 31st Marine Expeditionary Unit is capable of amphibious landings and overland assaults. The unit is onboard the USS Tripoli in the Arabian Sea and is also equipped to help with emergency evacuations, if needed.

82nd Airborne Division

Based in Fort Bragg, North Carolina, the 82nd Airborne Division trains to be able to deploy overseas with 18 hours notice. The soldiers can parachute into combat, or launch an overland assault. In late March, Trump ordered about 2,000 soldiers of the 82nd Airborne’s Immediate Response Force sent to the Middle East. The unit is still in the region, housed at an undisclosed base.

Special Operations Forces

There are U.S. special operations forces located on bases around the Middle East. The Air Force Pararescue jumpers, Navy SEALS, and the Army’s Delta Force were used in the missions to rescue two U.S. aviators shot down inside Iran in early April, and similar units were part of the complex mission to capture the Venezuelan leader Nicolás Maduro in January. Those elite units are still on call in the Middle East and ready to deploy if ordered.