In the Persian Gulf, about 20 miles off the Iranian coast, is a small, rocky island called Kharg that could be the Trump administration’s key to victory in the war it unleashed. It could also be America’s undoing.The island is tiny—a little less than eight square miles—and has a population of about 20,000 people, most of them oil workers. It’s also the point of departure for approximately 90 percent of Iran’s oil exports. The United States struck military targets on Kharg on March 13 and is now reportedly considering invading it.The thinking goes something like this: Iran has extended its control over the world’s oil markets by effectively closing the Strait of Hormuz, a waterway through which most Persian Gulf exports must travel. The Iranian regime has made an exception for tankers carrying its own oil, and has reportedly exported at least 16 million barrels since the war began. But other Gulf nations have been largely unable to move their oil, and the effect has been an increase in Iranian revenue as the price of crude oil goes higher. The Iranians have reinforced this outcome by targeting pipelines on the Arabian Peninsula, which bypass the Strait of Hormuz. And the Iran-allied Houthis in Yemen have the capacity, if they so choose, to shut down the Bab el-Mandeb Strait, between the Red Sea and the Gulf of Aden, potentially closing off the Suez Canal.[Rogé Karma: Iran might use its economic-doomsday option]That Iran might close the Strait of Hormuz has long been considered a risk of taking military action against the Islamic Republic. But the Trump administration seems to have presumed that the closure would hurt Iranian oil exports, too—leading to economic crisis and possibly even regime collapse. Instead, Iran is continuing to export oil, which helps prop up its wobbly economy and allows the regime to fight another day.The Islamic Republic’s theory of victory is that Iran can absorb American and Israeli air strikes longer than America can endure the economic pain and pressure of the strait being closed. If the Gulf states and others whose commerce has been disrupted are hurt badly enough, they may urge the United States to end the war, even on terms relatively favorable to Iran. The rise of gas prices, and the prices of other consumer goods, could also push the Trump administration to seek to end the conflict well ahead of the midterm elections in the United States.Taking Kharg would give the United States an important bargaining chip and undermine Iran’s theory of victory. Unable to export most of its oil, Iran would come under much the same kind of pain and pressure that it is attempting to inflict by closing the strait. The U.S. might then continue its air campaign until Iran decides to accept American terms for ending the war, rather than continue to suffer economic devastation.This may be why last week the United States dispatched the 31st Marine Expeditionary Unit from Japan to the Middle East. The unit operates from the USS Tripoli, an America-class amphibious-assault ship that reportedly carries a rapid-response force of 2,200 to 2,500 Marines. Moving such a unit to a different theater is not a thing done lightly, and the number of troops involved—enough for the island but not enough to seize the Iranian side of the strait—strongly suggests that the United States has designs on Kharg.An invasion of Kharg would likely be preceded by air strikes against any remaining military targets on the island, as well as those capable of threatening the island from the Iranian mainland. The Persian Gulf is still too dangerous for U.S. warships to enter, so the Tripoli would probably remain at a distance, sending Marines ashore by means of MV-22 Ospreys. Their first goal would be to seize the facilities that could allow Iran to bring in troops and heavy equipment, such as the 5,922-foot runway at Kharg airport. The United States would provide extensive air support to quickly eliminate pockets of resistance.The United States could probably take Kharg Island relatively quickly. But holding it would be much more difficult and could turn deadly. Iran might order its forces to set the oil facilities there on fire, much as Saddam Hussein did with Kuwait’s oil fields in the Gulf War, contaminating the area and sickening U.S. troops. On the small island of Kharg, U.S. forces would have less access to the equipment they would need to deal with this problem than their predecessors did in Kuwait, and they couldn’t easily move away or upwind from the fires.But even without such tactics, the Iranians could make holding Kharg very difficult. The operation would likely take longer than 15 days, which is about how long an expeditionary unit can operate without logistical support. Kharg is far—140 miles—from American assets in Kuwait City, but very close to Iran’s coast. Resupply vessels would be exposed not only to cruise-missile fire but also to Iran’s “mosquito fleet,” which includes robotic drones, sometimes called unmanned surface vessels (Ukraine used similar devices to bottle up the Russian Black Sea fleet at Novorossiysk).Resupply missions by air would be risky too. Kharg’s distance from Kuwait means that American air defenses there would likely consist of only the shoulder-fired MANPADS that the Marines would probably carry and patrols of U.S. fighter planes. These can intercept drones but not ballistic missiles. And Iran could use its ballistic missiles to crater the runway at Kharg, preventing U.S. cargo aircraft from landing there. Tehran probably lacks the capacity to do this with a long-range precision strike, but Kharg lies within the range of its numerous short-range ballistic missiles. A barrage of these would need to land just one lucky strike to make the runway unusable. Oil fires, if they were to occur, could make air access to the island even more difficult.The final threat is one suggested by experiences in Ukraine. Russia has been using loitering munitions—drones that hover over a territory, scanning for targets that they then dive in to destroy—to great effect. Called Lancets, these cost about as little as Shahed drones, and Iran could employ them over Kharg to seek out resupply ships and aircraft in the process of loading or unloading, as well as vehicles and troops. To guard against loitering munitions has required Ukraine to cover entire road systems with nets. In April 2024, Iran unveiled its own version of the Lancet. This could be a fake meant to boost domestic morale—Iran has done that sort of thing in the past—but if it’s real, it could cause real problems.[Eliot A. Cohen: One war, two mistakes]U.S. troops may well take Kharg Island, only to endure ballistic-missile strikes, drone attacks, and petrochemical smoke, all without a reliable means of obtaining logistical support. The result could be a grinding war of attrition that more closely resembles the battle space in Ukraine than it does the “shock and awe”–style campaigns that Americans are used to. Iran has given every indication that it would likely escalate by striking oil-and-gas facilities in the region, just as it did to Qatar and Saudi Arabia after the Pars South gas field was struck. Ground casualties and the destruction of oil infrastructure throughout the region would almost certainly create pressure on Donald Trump to pull out; but extracting troops under loitering munitions is dangerous, and aircraft on the ground are prime targets for these circling drones.Conversely, if the United States managed to take and hold onto Kharg, the Iranian regime could find itself without the means to export its oil and unable to survive. Iran would then be forced to give the United States some—even much—of what it wants in exchange for control of the island.That’s one way for Trump to get the off-ramp he desires. But his administration has never tried anything like this. An operation that involves taking land inside an adversary’s territory and then holding it until the cessation of hostilities involves a whole new world of risk—and an escalation to which Iran is sure to respond.