After suffering a heavy setback at the Battle of Vĩnh Yên, Giáp decided to attack the port of Hải Phòng, the centerpiece of French logistics.

The Mạo Khê coal mine was located 1,000 meters (3,300 feet) to the north of the town and was garrisoned by a company of partisans commanded by a Vietnamese lieutenant and three French NCOs.

At this point, the anticipated communist attack stalled under heavy pressure from French naval forces, which had managed to approach Mạo Khê via a deep channel in the nearby Đà Bắc River.

[2][3] De Lattre was uncertain of Giáp's intentions, but he did send the 6th Colonial Parachute Battalion (6e BPC) and some artillery batteries to relieve the beleaguered forces at Mạo Khê.

Early in the morning of 27 March, the Việt Minh 209th Regiment of the 312nd Division launched a massive attack against the coal mine, whose defenders resisted until French B-26s and Hellcats alleviated the pressure.