 Complete the following phrase:  The Battle of Nghĩa Lộ was a battle of the First Indochina War. In the fall of 1952 the French army encountered its most serious crisis since the disasters near the Chinese border Chiến dịch biên giới  Borderland Campaign at Cao Bằng, Đông Khê and RC 4 occurred in 1949 and 1950. The Battle of Nghĩa Lộ was the opening salvo in a series of offenses and counter-offenses in late 1952 during the First Indochina War. It was part of a Việt Minh offensive in the Tai region of Tonkin in the vicinity of the Black River Northwest Campaign or Black River Offensive. The French countered with Operation Lorraine to attack Việt Minh rear supply bases in an attempt to cut off the offensive. The Việt Minh did not cease or divert the offensive to protect its supply bases. The Việt Minh continued its offensive attack against 