The British shared these conflicting fears and hopes, but they had built a nuclear weapon of their own. For a delivery system, they arranged to buy the air-tosurface Skybolt missile from the United States. But McNamara, in a fight with the U.S. Air Force, canceled Skybolt, and this precipitated a crisis in British -- American relations that was calmed only by a summit meeting between Prime Minister Macmillan and President Kennedy at Nassau. There they agreed that the United States would sell the United Kingdom the Polaris missile, which was launched from submarines. For the British it proved an ideal solution. It gave them an independent nuclear retaliatory force, and it was comparatively very cheap.
A number of "good" reasons why the British should have an independent nuclear force were offered at various times, but the "real" reason was what was bothering the other Allies: When a crisis came, would the United States stand firm in its threat to retaliate against the Soviet homeland with nuclear weapons if the Soviets attacked one of the European Allies? The United Kingdom stayed in the NATO alliance, but it provided what the British called "a second decision-centre," in case the first decision-center, the United States, backed down.
The French reached the same conclusion -- to build their own independent nuclear deterrent, the force de frappe. But France decided not to remain as a full member of NATO and forced NATO to move its headquarters to Belgium. De Gaulle admitted that France could not defeat the Soviet Union by itself. His argument was that the enemy would be deterred by the certainty that France had the power "to tear off an arm as he goes by."