But since the collapse of the Soviet Union, Britain has taken several steps toward reducing its arsenal, while categorically stating it will maintain some nuclear force. The final step in Britain's nuclear reduction took place after the election of Labor leader Tony Blair as prime minister.

Seeking to reduce the costs of maintaining the British military, the Blair government outlined a streamlined and reduced nuclear arsenal in 1998 that packed 70 percent less punch than the nation boasted during the Cold War.

The British government now possesses approximately 200 nuclear warheads. It has four submarines capable of launching a nuclear missile strike, but only one is on patrol at any given time. Additionally, the Labor government decided to reduce the number of missiles aboard each sub to 20 and none are targeted at a specific site.

By the end of 1998, the U.K. had also moved to completely denuclearize its air force and reduced the number of planned missile purchases from the United States from 65 to 58 Trident sub-launched missiles.

With its decision to eliminate the Royal Air Force squadrons capable of launching a nuclear strike, Britain's nuclear arsenal can only be launched from one of its four nuclear missile submarines. But the British government has maintained that the current global situation requires that it maintain a nuclear deterrent.

"[T]he continuing risk from the proliferation of nuclear weapons, and the certainty that a number of other countries will retain substantial nuclear arsenals, means that our minimum deterrent capability, currently represented by Trident, is likely to remain a necessary element of our security for the present," Foreign Office Minister Bill Rammell told the House of Commons in March 2004.

The government has, at times, had to fight its own Labor Party over nuclear weapons, arguing that Britain must retain an active nuclear arsenal to create a deterrent to those who might attack, including terrorists.

"Conditions of extreme self defense are extraordinarily difficult to contemplate but we must reserve the right to use our nuclear weapons in those circumstances, otherwise clearly they cannot act as the deterrent that they are," Minister of Defense Geoff Hoon said on the eve of the Iraq war.

The British government has made the case that its desire is to maintain a nuclear arsenal capable of a "substrategic" mission.

The Bulletin of the Atomic Scientists quotes a British defense ministry official as describing a substrategic strike as "the limited and highly selective use of nuclear weapons in a manner that fell demonstrably short of a strategic strike, but with a sufficient level of violence to convince an aggressor who had already miscalculated our resolve and attacked us that he should halt his aggression and withdraw or face the prospect of a devastating strategic strike."

This policy is the latest of a nuclear weapons program as old as any other nation, for although Britain was the third nation to develop a usable nuclear weapon, its scientists were the first to theoretically design a fission bomb in the early days of World War II. The work, shared with the United States and largely stolen by the Soviet Union, paved the way for the development of the first generation of atomic weapons. For much of its early work, British scientists paired with United States research teams.

But in the days after the war, and after the election of the opposition Labor government, the British government decided it would also develop an independent program, free of the Americans.

To build its program, the British government relied mostly on the work and memory of one scientist, William Penney. Penney had worked in the Los Alamos Laboratory in New Mexico with the Americans developing the first atomic weapons used to end World War II.

Once the British government had agreed to develop its own program, it turned to Penney to design the weapon and assist with the program to build it. For the British, it remained a politically important development in the early 1950s to develop its own bomb program if it were to remain one of the world's great powers.

Then Prime Minister Harold Macmillan explained the government's rationale, saying as the British hydrogen bomb tests began in 1957, "We have made a successful start. When the [nuclear] tests are completed, as they soon will be, we shall be in the same position as the United States or Soviet Russia. We shall have made and tested the massive weapons. It will be possible then to discuss on equal terms."

		British Archives Britain's first nuclear test off the coast of Australia.

The British tests, centered often in or off the coast of Australia, proceeded throughout the 1950s. The testing included atomic weapons, free-fall bombs, tactical weapons and, by 1957, thermonuclear devices.

The British nuclear program underwent a major shift at the end of the 1950s. Having proved it could develop thermonuclear weapons, Britain was approached again by the United States. The Americans wanted a strategic partnership that would carefully combine nuclear development, testing and deployment to better deter the Soviets.

Thus, British work to build later versions of its warheads was aided by American engineering and vice versa. The two countries also combined their testing programs, continuing to share information on tests up until the 1990s.

Despite the end of nuclear tests, the two nations have continued to partner closely. When the British wanted to upgrade its missile systems for launching nuclear weapons, it turned to the Americans to purchase newer Trident missiles.

-- Compiled by Lee Banville for the Online NewsHour