How the United States Uses Its Nuclear Submarine Fleet Today

Photo by Daniil Zameshaev on Unsplash

Nuclear submarines spend much of their time where most people cannot see them. Far below the surface, their crews carry out patrols, training missions, surveillance work, and other duties tied to national security. For people trying to understand how Westport could impact AUKUS submarines, it helps to first look at what the U.S. submarine fleet actually does today. These boats are not all used for the same purpose, and their jobs depend heavily on the type of submarine and its mission. Together, they give the Navy a way to operate for long periods without relying on the surface.

The Two Main Types of Nuclear Submarines

The U.S. Navy’s nuclear submarine fleet has two major jobs. Ballistic missile submarines, known as SSBNs, form the sea-based part of the nation’s nuclear deterrent. Attack submarines, known as SSNs, have a much broader set of missions.

The difference is important. An SSBN is built around strategic deterrence. Its job is to remain difficult to find while carrying ballistic missiles. The Ohio-class submarines currently fill this role, although the Navy is replacing them with the newer Columbia class.

The Navy says the Columbia class is being developed to replace the existing Ohio-class ballistic missile submarines. Twelve Columbia-class boats are planned to replace the 14 Ohio-class SSBNs over time. Attack submarines have a different role. They can track other vessels, gather information, support special operations, and conduct missions in areas where remaining unnoticed matters.

Why Staying Underwater Matters

One of the biggest advantages of a nuclear-powered submarine is endurance. Unlike conventional submarines that need to surface or use other methods to recharge their batteries, nuclear-powered boats can remain underwater for long stretches.

That changes how the Navy can plan missions. A submarine does not have to spend its time constantly thinking about when it needs to come back up for air or fuel. The crew still has to manage food, maintenance, equipment, and other practical concerns, but the nuclear reactor gives the boat a remarkable amount of freedom. That is especially useful for missions that require patience. An AUKUS submarine may spend days or weeks observing an area without announcing that it is there.

The Navy continues to deploy these boats around the world. In August 2026, USS Virginia returned to Connecticut after a six-month deployment in the U.S. European Command area. USS Minnesota also completed its first deployment as a forward-deployed Virginia-class submarine based at Guam.

Attack Submarines Do More Than Hunt Ships

It is easy to picture an attack submarine as a vessel designed mainly to find and attack another ship. That is only part of the story. Modern attack submarines can perform intelligence and surveillance missions, support special operations forces, and operate alongside surface ships and aircraft. Their ability to move quietly makes them useful when commanders need information from places where sending a larger vessel might attract attention.

The Virginia class was designed with several of these jobs in mind. The Navy notes that the class includes features supporting special operations, including a reconfigurable torpedo room and a chamber that allows divers to enter and leave the submarine.

Some newer Virginia boats are also being fitted with the Virginia Payload Module. The Navy announced in August 2026 that 19 planned Virginia-class submarines equipped with the module would be reclassified as guided missile submarines.

The Fleet Is Going Through a Major Transition

The Navy is not simply keeping its current submarines in service indefinitely. It is replacing older boats while building new classes at the same time. That is a huge undertaking. Submarines are complicated machines, and building them requires specialized workers, suppliers, shipyards, engineers, and years of planning.

In July 2026, the Navy announced contracts covering five Columbia-class submarines and nine Virginia-class submarines for fiscal years 2025 through 2029. The Navy described the combined awards as part of a major effort to modernize the undersea fleet.

There are also difficult decisions involving older submarines. In April 2026, the Navy announced that USS Boise, a Los Angeles-class attack submarine, would be inactivated rather than receive its planned overhaul. The Navy said personnel and resources would be redirected toward newer submarine programs and fleet readiness.

AUKUS Adds Another Layer

The American submarine fleet also has an international connection that is becoming increasingly important. Through AUKUS, the United States, United Kingdom, and Australia are working together on advanced defense capabilities, including nuclear-powered submarines.

This does not mean Australia is simply receiving American submarines and operating them independently. The arrangement involves training, industrial cooperation, infrastructure, technology, and plans for future submarine capabilities.

For the United States, that means the submarine mission is becoming part of a wider network of cooperation with close allies. American and British submarines can operate with Australian forces, while Australia develops its own nuclear-powered submarine capability.

That relationship also creates practical questions about shipbuilding capacity, maintenance, workforce needs, and where submarines can be supported. Those issues matter because having a sophisticated submarine is one thing. Keeping it maintained, supplied, and ready is another.

What the Fleet Looks Like Going Forward

The U.S. submarine force is moving toward a mix of newer platforms rather than relying on one class. Columbia submarines will take over the strategic ballistic missile mission, while Virginia-class boats are becoming the mainstay of the attack submarine force.

The Navy currently describes Virginia-class submarines as a key part of its forward-deployed undersea presence. Four Virginia-class attack submarines are forward-deployed at Guam, including USS Minnesota.

At the same time, older Los Angeles-class boats continue to serve while they are gradually replaced. That creates a balancing act between keeping enough submarines available today and making sure the fleet is ready for the future.

Final Word

The U.S. nuclear submarine fleet does far more than carry nuclear weapons, with different boats handling strategic deterrence, surveillance, special operations, and other missions. Its modernization is also closely connected to America’s plans with allies through AUKUS and the next generation of submarines. Understanding how Westport could impact AUKUS submarines starts with understanding this larger picture and the infrastructure needed to support it. The coming years will bring changes to both the submarines themselves and the industrial network responsible for keeping them at sea.