Operations in Tonkin French victories in the delta Meanwhile, the French army in Tonkin was also putting severe pressure on the Chinese forces and their Black Flag allies. General Millot, whose health was failing, resigned as general-in-chief of the Tonkin expeditionary corps in early September 1884 and was replaced by General Brière de l'Isle, the senior of his two brigade commanders. Brière de l'Isle's first task was to beat off a major Chinese invasion of the Red River Delta. In late September 1884, large detachments of the Guangxi Army advanced from Langson and probed into the Lục Nam valley, announcing their presence by ambushing the French gunboats Hache and Massue on 2 October. Brière de l'Isle responded immediately, transporting nearly 3,000 French soldiers to the Lục Nam valley aboard a flotilla of gunboats and attacking the Chinese detachments before they could concentrate. In the Kép Campaign, (2 to 15 October 1884), three French columns under the overall command of General de Négrier fell upon the separated detachments of the Guangxi Army and successively defeated them in engagements at Lam Cốt (6 October), Kép (8 October) and Chũ (10 October). The second of these battles was marked by bitter close-quarter fighting between French and Chinese troops, and de Négrier's soldiers suffered heavy casualties storming the fortified village of Kép. The exasperated victors shot or bayoneted scores of wounded Chinese soldiers after the battle, and reports of French atrocities at Kép shocked public opinion in Europe. In fact, prisoners were rarely taken by either side during the Sino-French War, and the French were equally shocked by the Chinese habit of paying a bounty for severed French heads. In the wake of these French victories the Chinese fell back to Bắc Lệ and Đồng Sông, and de Négrier established important forward positions at Kép and Chũ, which threatened the Guangxi Army's base at Lạng Sơn. Chũ was only a few miles southwest of the Guangxi Army's advanced posts at Đồng Sông, and on 16 December a strong Chinese raiding detachment ambushed two companies of the Foreign Legion just to the east of Chũ, at Hà Hồ. The legionnaires fought their way out of the Chinese encirclement, but suffered a number of casualties and had to abandon their dead on the battlefield. De Négrier immediately brought up reinforcements and pursued the Chinese, but the raiders made good their retreat to Đồng Sông. Shortly after