be difficulties in enforcing the accord, but nothing specific was said. The French assumed that the Chinese troops would leave Tonkin as agreed, and made preparations for occupying the border towns of Lạng Sơn, Cao Bằng and Thất Khê. In early June 1884 a French column under the command of Lieutenant-Colonel Alphonse Dugenne advanced to occupy Lạng Sơn. On 23 June, near the small town of Bắc Lệ, the French encountered a strong detachment of the Guangxi Army ensconced in a defensive position behind Thương River. In view of the diplomatic significance of this discovery, Dugenne should have reported the presence of the Chinese force to Hanoi and waited for further instructions. Instead, he gave the Chinese an ultimatum, and on their refusal to withdraw resumed his advance. The Chinese opened fire on the advancing French, precipitating a two-day battle in which Dugenne's column was encircled and seriously mauled. Dugenne eventually fought his way out of the Chinese encirclement and extricated his small force. When news of the Bắc Lệ ambush reached Paris, there was fury at what was perceived as blatant Chinese treachery. Ferry's government demanded an apology, an indemnity, and the immediate implementation of the terms of the Tianjin Accord. The Chinese government agreed to negotiate, but refused to apologise or pay any indemnity. The mood in France was against compromise, and although negotiations continued throughout July, Admiral Courbet was ordered to take his squadron to Fuzhou (Foochow). He was instructed to prepare to attack the Chinese Fujian Fleet in the harbour and to destroy the Foochow Navy Yard. Meanwhile, as a preliminary demonstration of what would follow if the Chinese were recalcitrant, Rear Admiral Sébastien Lespès destroyed three Chinese shore batteries in the port of Keelung in northern Formosa (Taiwan) by naval bombardment on 5 August. The French put a landing force ashore to occupy Keelung and the nearby coal mines at Pei-tao (Pa-tou), as a 'pledge' (gage) to be bargained against a Chinese withdrawal from Tonkin, but the arrival of a large Chinese army under the command of the imperial commissioner Liu Mingchuan forced it to re-embark on 6 August. The Sino-French War, August 1884 to April 1885 Operations of Admiral Courbet's squadron Fuzhou and the Min River Negotiations between France and China broke down in mid-August, and on 22 August Courbet was ordered to attack the Chinese fleet at Fuzhou. In the Battle of Fuzhou