Ballistic missile submarines (SSBNs) are a type of military submarine designed to carry and launch nuclear ballistic missiles. They operate stealthily underwater, making them difficult to detect, which enhances their strategic deterrent capabilities. SSBNs are a key component of a nation's nuclear triad, providing a second-strike capability in case of a nuclear attack. These submarines are typically equipped with multiple missile launch tubes and can carry a variety of missiles, such as the Trident II. They are often deployed by major naval powers, including the United States, Russia, and China, to ensure a credible and survivable nuclear deterrent.