Following their defeat of the French forces in the Battle of Dien Bien Phu, the main Viet Minh force at Dien Bien Phu began its march toward the Red River Delta area around Hanoi. On 19 May the 315th Troop Carrier Wing sent four C–46 Commandos and crews to Do Son to be on standby in case of emergency evacuation. On 27 May, the planes began daily courier flights to Tourane.