Editing Battle of Dien Bien Phu (section)

=== Establishment of air operations ===
{{Further|Operation Castor}}
[[File:Dien Bien Phu001.jpg|thumb|250px|Colonel [[Christian de Castries]], French commander at Điện Biên Phủ]]

Operations at Điện Biên Phủ began at 10:35 on 20 November 1953. In ''Operation Castor'', the French dropped or flew 9,000 troops into the area over three days, as well as a bulldozer to prepare the airstrip. They were landed at three drop zones: "Natasha" (northwest of Điện Biên Phủ), "Octavie" (to the southwest), and "Simone" (to the southeast).{{sfn|Davidson|1988|p=194}} The Viet Minh elite 148th Independent Infantry Regiment, headquartered at Điện Biên Phủ, reacted "instantly and effectively". Three of its four battalions, however, were absent.{{sfn|Davidson|1988|p=193}} Initial operations proceeded well for the French. By the end of November, six parachute battalions had been landed, and the French Army consolidated its positions.

It was at this time that Giáp began his countermoves. He had expected an attack but had not foreseen when or where it would occur. Giáp realized that, if pressed, the French would abandon [[Lai Châu Province]] and fight a [[pitched battle]] at Điện Biên Phủ.<ref name="Davidson_p196">{{harvnb|Davidson|1988|p=196}}</ref> On 24 November, Giáp ordered the 148th Infantry Regiment and the [[316th Division (Vietnam)|316th Division]] to attack Lai Chau, while the [[308 Division (Vietnam)|308th]], [[312th Division (Vietnam)|312th]], and [[351st Artillery-Engineer Division (Vietnam)|351st]] divisions assaulted Điện Biên Phủ from ''[[Việt Bắc]]''.<ref name="Davidson_p196" />

Starting in December, the French, under the command of Colonel [[Christian de Castries]], began transforming their anchoring point into a fortress by setting up seven satellite positions. (Each was said to be named after a former mistress of de Castries, although the allegation is probably unfounded, as the eight names begin with letters from the first nine of the alphabet.) The fortified headquarters was centrally located, with positions ''Huguette'' to the west, ''Claudine'' to the south, and ''Dominique'' to the northeast.<ref name="Davidson, p. 199">{{harvnb|Davidson|1988|p=199}}</ref> The other positions were ''Anne-Marie'' to the northwest, ''Beatrice'' to the northeast, ''Gabrielle'' to the north, and ''Isabelle'' {{convert|6|km|abbr=on}} to the south, covering the reserve airstrip.{{sfn|Windrow|2004|p=312}}

The arrival of the 316th Viet Minh Division prompted Cogny to order the evacuation of the Lai Chau garrison to Điện Biên Phủ, exactly as Giáp had anticipated. En route, they were virtually annihilated by the Viet Minh. "Of the 2,100 men who left Lai Chau on 9 December, only 185 made it to Điện Biên Phủ on 22 December. The rest had been killed, captured, or "deserted".{{sfn|Davidson|1988|p=203}}

French military forces had committed 10,800 troops, together with yet more reinforcements, totalling nearly 16,000 men, to the defense of a monsoon-affected valley surrounded by heavily-wooded hills and high ground that had not been secured. Artillery as well as ten US [[M24 Chaffee]] light tanks (each broken down into 180 individual parts, flown into the base, and then re-assembled) and numerous aircraft (attack and supply types) were committed to the garrison. A number of quadruple 0.50 calibre machine guns were present and used in the ground role.<ref name=autogenerated1>''Dien Bien Phu: The Epic Battle America Forgot'' by Howard R. Simpson (a US diplomat)</ref> This included France's regular troops (notably elite paratrooper units, plus those of the artillery), French [[French Foreign Legion|Foreign Legionnaires]], Algerian and Moroccan [[tirailleur]]s (colonial troops from North Africa) and locally-recruited Indochinese (Laotian, Vietnamese and Cambodian) infantry.{{sfn|Windrow|2004|pp=303–308}}

In comparison, altogether the Viet Minh had moved up to 50,000 regular troops into the hills surrounding the French-held valley, totalling five divisions, including the 351st Heavy Division, which was an artillery formation equipped with medium artillery, such as the US [[M101 howitzer|M101]] 105mm howitzer, supplied by the neighbouring People's Republic of China (PRC) from captured stocks obtained from defeated [[Republic of China (1912-1949)|Nationalist China]] as well as US forces [[Korean War|in Korea]], together with some heavier field-guns as well as anti-aircraft artillery.<ref name="d223">{{harvnb|Davidson|1988|p=223}}</ref> Various types of artillery and anti-aircraft guns (mainly of Soviet origin), which outnumbered their French counterparts by about four to one,<ref name="d223" /> were moved into strategic positions overlooking the valley and the French forces based there. The French garrison came under sporadic direct artillery fire from the Viet Minh for the first time on 31 January 1954 and patrols encountered the Viet Minh troops in all directions around them. The French were completely surrounded.{{sfn|Davidson|1988|p=220}}