This article places 1907 Hague Convention VIII in its historical context, examines its content, summarizes State practice since 1907 (including during the two World Wars) and discusses the Convention’s relevance to contemporary mine warfare. The Convention has inherent shortcomings, has never been strictly applicable in any war since 1907, and is not strictly relevant to anything other than automatic contact mines (effectively excluding modern influence mines). Despite this—and a paucity of substantial State practice since 1945—the conclusion is that the Convention has influenced the customary law on sea-mines. When that custom was combined with other relevant custom (particularly that pertaining to the peacetime law of the sea) during the San Remo Manual process, the result was an extremely useful guide to what would probably be acceptable in relation to mine warfare. There is now evidence that the San Remo Manual mine warfare articles are themselves becoming accepted as custom.