On 20 November 1953 Bigeard and his unit took part in Operation Castor, the opening stage of the Battle of Dien Bien Phu. Bigeard and the 6e BPC returned to Dien Bien Phu on 16 March 1954, parachuting in to reinforce the now besieged garrison. He acted as deputy to Pierre Langlais, and was a member of the "parachute mafia" – a unit of the high-ranking paratroopers at the camp who oversaw combat operations. Historian Bernard Fall asserts that an armed Bigeard, along with Langlais, took "de facto" command of the camp from General Christian de Castries in mid-March. The historian Jules Roy, however, makes no mention of this event, and Martin Windrow argues that the 'paratrooper putsch' is unlikely to have happened. Both Langlais and Bigeard were known to be on good relations with their commanding officer.