Three Trident II D5 missiles were launched by a U.S. Navy ballistic missile submarine to validate their accuracy and performance.

The unarmed missiles were fired over a three-day period by an Ohio-class vessel at sea, flew over the sea and landed in the sea, the Navy said, completing a Follow-on Commander's Evaluation Test.

"A credible, effective nuclear deterrent is essential to our national security and the security of U.S. allies and friends," the Navy said. "Strategic weapons tests, exercises and operations such as FCET-52 demonstrate the readiness of the submarine launched Trident II missile. As the most survivable leg of our strategic deterrent Triad, it provides the national command authority with assured second-strike capability."

Trident is a key part of the U.S. strategic deterrent. It is a submarine-launched ballistic missile with multiple, independently targetable re-entry vehicles with thermonuclear warheads.

The test firings were the 158th, 159th, and 160th successful test flights of the Trident II D5 missile.