wanted to stabilize the situation so that they could begin peace negotiations on favorable terms: military victory was no longer an objective. Navarre's instructions were to insure the safety of the troops under his command. Instead, he undertook Operation Castor on 20 November 1953. Five French battalions parachuted into Điện Biên Phủ in the Mường Thanh Valley, a 20-km-long, 6-km-wide basin surrounded by hills. Navarre hoped to draw the Viet Minh into a pitched battle where he hoped to defeat them. Authorities in France did not learn of the operation until six hours after it started. Things went wrong almost immediately. The French position came under heavy, unanticipated artillery fire from the surrounding hills. Troops were unable to execute any missions beyond the valley floor, limiting actions to patrols and local counterattacks. It became increasingly difficult to bring in supplies by air, or to provide air support. After intelligence reports on 3 December 1953 showed four enemy Divisions closing on Điện Biên Phủ, Navarre issued instructions accepting battle and calling for Điện Biên Phủ to be held at all costs. By January 1954 he started exploring plans for withdrawal. He soon realized any breakout attempt would be suicidal. No significant attempt to break out was ever made. Complicating the situation, Navarre initiated a second offensive operation on 12 December 1953, committing nearly twice as many troops to Operation Atlante in south central Vietnam, over 400 miles from Điện Biên Phủ. Navarre saw Operation Atlante as his main effort; he did not believe that Điện Biên Phủ would be a decisive operation. He even speculated that the loss of Điện Biên Phủ Dien was strategically acceptable. Navarre failed to consider the devastating effect the loss would have on Army morale, and the resulting loss of political support for the war at home. By 13 March 1954 the attack on Điện Biên Phủ had begun. The French garrison numbered about 13,000; the Viet Minh massed more than 50,000 men. After some initial success, Operation Atlante quickly bogged down into a series of Viet Minh ambushes on French convoys. The French eventually terminated Operation Atlante with no tangible gains while Điện Biên Phủ was lost on 7 May 1954, after a siege of 54 days. Peace talks began in Geneva the next morning. Any negotiating advantage the French government had expected had been lost by Navarre's miscalculations. The First Indochina War was over.