The U.S. Navy has reported on Friday that has Ohio class of nuclear-powered submarine tested four life-extended Trident II D5 missiles to validate their performance.

“The U.S. Navy conducted four scheduled missile test flights of unarmed Trident II (D5) missiles from USS Nebraska (SSBN-739), an Ohio-class ballistic missile submarine, off the coast of Southern California this week,” a service news release states.

The first two launches took place Sept. 4, and the last two were Sept. 6. All occurred before sunrise.

These test flights were part of a Commander Evaluation Test (CET) whose primary goal was to validate performance expectations of the life-extended Trident II (D5) strategic weapon system.

These launches mark 176 successful flights of the Trident II (D5) strategic weapon system. CETs and other flight tests are conducted on a recurring, scheduled basis to evaluate and ensure the continued reliability and accuracy of the system. The missile tests were not conducted in response to any ongoing world events.

“Our nation’s sea-based deterrent has been a critical component of ournational security since the 1960s, and this week’s launches continue to demonstrate the credibility and reliability of our life-extended missiles,” said Vice Adm. Johnny R. Wolfe, director of the Navy’s Strategic Systems Programs, the command responsible for the Navy’s strategic weapons.

The Trident II (D5) strategic weapon system, originally designed with a life span to 2024, recently underwent a life extension that will keep it operational through the late 2040s. The life-extended missiles will serve for the remaining service life of U.S Ohio-class and United Kingdom Vanguard-class SSBNs, and as the initial loadout for the U.S. Columbia-class and U.K. Dreadnought-class SSBNs.

The life extension program addressed potential aging and obsolescence issues. “The life extended missiles are now being deployed to the Fleet, but ourwork is not done,” Wolfe said.

“The nuclear deterrence mission is the Department of Defense’s No. 1 priority, and for the U.S. Navy that means not only maintaining our current capability, but also developing the next generation of Trident missiles and shipboard strategic weapon system that will ensure a credible sea-based deterrent for the next 40 years and beyond,” he added.

A credible, effective nuclear deterrent is essential to our national security and the security of U.S. allies. Deterrence remains a cornerstone of national security policy in the 21st century.

Strategic Systems Programs is the Navy command that provides cradle-to-grave lifecycle support for the sea-based leg of the nation’s nuclear triad. This includes training, systems, equipment, facilities and personnel responsible for ensuring the safety, security, and effectiveness of the nation’s Submarine Launched Ballistic Missile (SLBM) Trident II (D5) strategic weapon system.

SLBMs are one leg of the nation’s strategic nuclear deterrent triad that also includes the U.S. Air Force’s intercontinental ballistic missiles(ICBMs) and nuclear-capable bombers. Each part of the Triad provides unique capabilities and advantages. SLBMs make up about 70 percent of the U.S.’s deployed strategic nuclear deterrent Triad. The SLBM is the most survivable, provides persistent presence and allows flexible concept of operations.