The US aircraft carrier USS Gerald R. Ford is seen from a beach in Mallorca, Spain on October 4, 2025. | Clara Margais/picture alliance via Getty ImagesAs his latest threats to Iran suggest, President Donald Trump has become increasingly comfortable deploying military force around the world. But even with a military as large and technologically advanced as America’s, there are limits to how quickly he can simply pivot from one global crisis to another. Specifically, that limit seems to be about 30 knots — the top cruising speed of a Nimitz-class aircraft carrier. Due to maintenance and refueling needs, only about three of America’s 11 carriers are usually at sea at any given time, and keeping them too long in any one theater leaves others exposed. Trump’s overlapping military conflicts have been pushing these ships and their crews to their breaking point. Most recently, the fleet was whipsawed between far-flung rally points in Venezuela and Iran, requiring extraordinary measures and weeks of maneuvering to pivot between the two conflicts.Consider the long journey of the USS Ford strike group, which has been ordered to bolster the “massive Armada” Trump announced in January would assemble to pressure Iran. First it was rerouted from its Mediterranean mission in October to take part in the military buildup in the Caribbean that led to the capture of Venezuelan President Nicolas Maduro. Then, it was routed back to the Eastern Mediterranean as part of the Iran buildup over the public objections of the country’s top Naval officer amid concerns the nonstop deployment would disrupt everything from sailor morale to potential sewage system repairs. The Ford is now eight months into a twice-extended deployment that would normally last around six months, with little sign of relief in sight. The sheer logistical strain of moving and maintaining these massive ships is an under-appreciated part of the decision-making process around whether the US will go to war. When Trump backed off a red-line demand in January that Iran refrain from killing protesters or face military strikes, the lack of available carriers was likely a major factor. Now that he’s assembled more firepower in the region than any time since the 2003 invasion of Iraq, the punishing costs of keeping the fleet in place tilt the calculus in the other direction. The “use it or lose it” factor is one reason experts consider it highly likely that the president will ultimately order strikes rather than engage in extended diplomacy. What are aircraft carriers for?It’s striking that in an age when the trendy concepts in future military planning tend to revolve around cheap “attritable” systems, autonomy, and cyber, the default unit of American power, the main means by which the United States projects military force around the world, is still a 100,000 ton hunk of floating metal. It’s all the more notable given that there’s an ongoing and active debate over whether these ships are obsolete and will have a role in the wars of the future. “This is four-and-a-half acres of sovereign American soil that you can move anywhere in the world at 30-plus knots,” Hunter Stires, former maritime strategist to the secretary of the Navy, told Vox. “Naval power is the single most versatile and maneuverable element of national power that we have.”Hunter Stires, former maritime strategist to the secretary of the NavyStires points out that, as has been the case for centuries, there’s no substitute for the sea when it comes to moving stuff around the world quickly.“Naval power is the single most versatile and maneuverable element of national power that we have,” he said. “Thanks to the power of buoyancy, no other mode of transportation can move as much combat power as quickly or as cost effectively as ships can.”Still, one might wonder why we need all that combat power so close to the target. Operation Midnight Hammer, the bombing campaign against Iran’s nuclear facilities last June, was carried out by B-2 bombers that took off from Missouri and submarines launching Tomahawk missiles. We don’t know exactly what role the Ford played in the final operation to capture Maduro, but it involved aircraft taking off from dozens of locations, including in the continental US.Stacie Pettyjohn, an expert on military force design and director of the Center for a New American Studies, pointed out to Vox that while the US does have long-range bombers, its air forces “are predominantly short range tactical aircraft, so they have to be based in theater.” That means that in a longer-term campaign like the one that reporting suggests is now envisaged for Iran, “if they’re going to generate a lot of combat power, be able to fly a bunch of sorties, hit a lot of targets,” they need a place to land. Carrier are therefore invaluable, particularly given that a number of US allies in the region have said they don’t want their airspace used for an attack. Carrier strike groups also can play as much of a defensive as offensive role, as in the 12-day war with Iran last year, when they were vital in the effort to intercept Iranian missiles fired in retaliation for US and Israeli strikes.Beyond their combat role, Pettyjohn notes, carriers can be simply a “really visible, though, and strong signals that the US is actually making a credible threat to get involved.” As the White House pushes Iran to quickly agree to a deal limiting their nuclear capacity, and possibly ballistic missile programs, it’s a critical piece of leverage. Ultimately, the Venezuela operation and Midnight were short, limited operations. And initially, at least, the strikes on Iran may be that too. But the amount of combat power an aircraft carrier can generate, as well as the fact that it is a nuclear-powered craft that can stay at sea for years with resupply and maintenance, can be a message that the US is willing to be in it for the long haul. This is particularly true when, as is the case in the Middle East now, there are two carrier groups in theater, allowing for nearly continuous 24-hour operations. But there’s a cost to these buildups. Due to persistent conflicts in the Middle East, there have been times in recent years where there hasn’t been a single US carrier group deployed in the Pacific (There’s currently one, the George Washington.) “We are really robbing Peter to pay Paul in the Pacific,” Pettyjohn said.For this reason, some observers also questioned whether the use of a carrier was overkill in Venezuela given that they’re more typically associated with fighting wars against great powers like Russia and China, or well-armed and advanced militaries like Iran.“As a general rule: Carrier Strike Groups should be principally deployed to face down adversaries which require a Carrier Strike Group level of whoopass,” Stires said.Still ruling the waves?There are continual debates in defense circles about whether these giants still have a role in a world of hypersonic “carrier killer” missiles. In the wake of the successful use of drones on the battlefield and the seas in the war in Ukraine, many of the US plans for deterring a Chinese attack on Taiwan have focused on the concept of “attritable mass” — small, cheap drones basically — that integrate AI and can be quickly replaced.Pettyjohn notes however, that the systems that have proven so effective in Ukraine generally don’t have the kind of range and firepower that would make them effective in a war in the Pacific. US Naval planners have also put a heavy emphasis in recent years on the need for smaller cheaper combat ships to keep up with the rapid growth of China’s navy. The Trump administration appears to be moving in the opposite direction, however, recently announcing a new Trump-class battleship — three times the size of current US Destroyers and envisioned as an update of the World War II era battleships that modern aircraft carriers phased out. For the moment, however, aircraft carriers remain the most prominent and visible symbol of American military power. And their scarcity is one of the most important limits on the president’s ability to use that power wherever and whenever he wants.