Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Battle of Cao B ng was an ongoing campaign in northern Indochina during the First Indochina War, between the French Far East Expeditionary Corps and the Vi t Minh, which began in October 1947 and culminated on September 3, 1949. Since the start of the conflict, Vi t Minh troops had ambushed French convoys along the Vietnam China border from the Gulf of Tonkin on a 147-mile route to a French garrison at Cao B ng, known as Route Colonial 4, or RC4. Repeated ambushes led to repeated French operations of increasing strength to reopen the road, including a costly mission by the Foreign Legion in February 1948. On July 25, 1948, the Cao B ng encampment was itself attacked and held out for three days with two companies defending against two battalions of Vi t Minh. A further 28 ambushes took place in 1948.