French interest in Keelung dated from February 1884, when Admiral Sébastien Lespès, the commander of France's Far East naval division, had recommended its occupation in the event of a war between France and China on the grounds that it could be easily seized and easily held.
On the morning of 5 August, after the Chinese rejected a French ultimatum to hand over their coastal defences, La Galissonnière, Villars and Lutin engaged and disabled Keelung's three coastal batteries.