France did not withdraw from NATO. What it did was to withdraw its forces from NATO's integrated military structure, starting with its Mediterranean fleet in 1959. In 1966, all French forces were removed from the integrated command, all foreign forces were told to leave France, and NATO's military headquarters were moved from near Paris to Mons, in Belgium.
NATO's military structure was created in the early 1950s when it was felt that in order to face up to the Soviet Union, NATO needed a proper military command structure of its own rather than relying on a variety of national forces. At that time France was part of this structure.
The withdrawal of France's military forces from NATO's command was initiated by President Charles de Gaulle, who was uncomfortable with the 'special relationship' between the USA and Britain. De Gaulle wanted France, while remaining a member of NATO, to have greater independence.
NATO is a political organisation as well as a military one, and France never withdrew from the political side. At the time of its withdrawal from the military structure, it reassured its NATO partners that it would take part in the defence of Western Europe in the event of a Soviet attack, and it retained forces in West Germany for this purpose. NATO accepted this compromise.
France retained its military independence until 2009, when President Nicolas Sarkozy chose the occasion of a summit celebrating NATO's 60th anniversary to bring France back into the command structure. Sarkozy was far more sympathetic to the United States than many of his predecessors, and felt that in the post–Soviet era France no longer needed to display its independence in the same way. He argued that in fact France was losing out by not being in the command structure, and wanted it to be more closely involved in the planning and command process.
The decision didn't change a great deal in practice. France already contributed the fourth largest number of troops to NATO (after the US, UK and Germany). It was committed (under the NATO treaty) to joint action if a member were attacked, and was taking part in NATO's war against the Taleban in Afghanistan. But the move did have considerable political, diplomatic and symbolic importance, as it signalled an end to the anomaly of one of NATO's biggest contributors being outside the command structure.
France hoped that its return to the NATO fold might persuade the United States to accept the idea of a European defence policy – as allowed for in the Maastricht Treaty, which laid down that the EU should develop policies that "might in time lead to a common defence."
France's nuclear deterrent has never been under NATO command, and is not now.
Most of this article is an edited version of one that appeared on the BBC website in March 2009.
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