The United Kingdom re-committed to centering its strategic nuclear deterrent on ballistic submarines equipped with Trident missiles in a government report released July 16. 

The report, called the Trident Alternatives Review, effectively upheld a posture outlined in a 2010 strategic defense review. The alternatives report was commissioned amid a disagreement between the governing Conservatives and coalition junior partner Liberal Democrats, who are skeptical about proceeding with plans to recapitalize the ballistic missile submarine fleet. 

“The U.K. government’s nuclear posture and commitment to the Trident system is clear and this review does not affect it,” the report said, while allowing the Liberal Democrats to continue to look at alternatives.

The report largely examined the possibility of building a cruise missile with a nuclear warhead, and the possibility of using ships, attack subs or long-range bombers as the key aspects for nuclear deterrence. It concluded that all of those platforms would be more vulnerable compared to the ballistic missile submarine and that developing a cruise missile to carry a nuclear warhead would be too costly.

The Royal Navy’s Vanguard-class of ballistic subs, like the U.S. Navy’s Ohio-class boomers, will start retiring in the late 2020s and both countries are gearing up for–and cooperating on–their replacement programs.

The United Kingdom’s commitment to the ballistic sub deterrent is critical for the U.S. Navy, as the two services–in part to share costs–are jointly developing a common missile compartment (CMC) for their next fleets of the submarines. Because of the delay in the Ohio-class replacement program, the first CMC will likely be tested on a U.K. sub.

The British currently operate four Vanguard submarines. The United States operates 14 Ohio-class subs and intends to replace them with 12. The Navy plans to begin construction on the first Ohio replacement in 2021, two years later than previously planned.

Earlier this year, the U.S. Navy exercised a $60-million dollar contract option with General Dynamics [GD] Electric Boat for the continued design and development of the CMC. If all options are exercised, the contract value could reach $776 million.