Battle of Son Tay

The Battle of Son Tay pitted the French expeditionary corps led by Admiral Courbet against allied troops of the Black Flags, Chinese soldiers, and Vietnamese imperial forces. The French objective was to capture the fortified town of Son Tay, a strategic bastion on the road to Hanoi. After two days of fierce assault, the French seized the town despite stubborn defense.

In the conquest of Tonkin, France faced mixed Chinese, Vietnamese, and irregular (Black Flag) forces refusing Western control. Son Tay was a major fortified strongpoint held by Liu Yongfu, leader of the Black Flags. France launched a major offensive to break this resistance and impose its authority over northern Vietnam.

The assault was conducted in two phases: on 14 December, the French took outposts and reduced outlying forts around the town. On 15 December, massive artillery bombardment preceded a frontal attack by colonial troops penetrating Son Tay from the south. Street fighting was violent, conducted house by house. Defenders withdrew toward Bac Ninh after suffering heavy losses.

The capture of Son Tay established French military authority over western Tonkin and opened the way to conquest of the Red River delta. It also escalated tensions with China, which supported the Black Flags: the Franco-Chinese War would officially break out in 1884. Admiral Courbet gained prestige and was called to direct subsequent operations in Annam and southern China.