Operation Royal Marine was a military operation in May 1940 of the Second World War, during the Battle of France (10 May – 25 June 1940). The British floated fluvial mines down rivers which flowed into Germany from France. The plan was to destroy German bridges, barges and other water transport. After several postponements insisted on by the French government, fearful of German retaliation, the operation began on 10 May 1940, when the German offensive in the west began. The mines caused some damage and delay to German river traffic on the Rhine from Karlsruhe to Koblenz and damaged bridges and protective barriers. Part of the plan was for Royal Air Force (RAF) bombers to drop the mines into rivers and canals on moonlit nights but this had hardly begun when the campaign ended. The success of the plot was nullified by the Allied defeat and the Franco-German Armistice of 22 June 1940. Background Despite the concerns of the French government during the Phoney War, over German air attacks and reprisals against French waterways, it was intended that the operation would take place simultaneously with Operation Wilfred, a scheme to mine the waters around Norway. The novelty of Operation Royal Marine was intended to divert American attention from the possible illegality of Operation Wilfred. Wilfred was to force German convoys transporting Swedish iron ore into international waters, where they could be attacked by the Royal Navy. Simultaneous attacks with fluvial (river) mines against Germany was intended to deflect criticism that the Allies were not making war on Germany but the small countries around it, that they claimed to be protecting. A decision of the Anglo French Supreme War Council was taken on 28 March 1940 to commence Operation Royal Marine on 4 April and the air-dropping of mines on 15 April. The decision was vetoed shortly afterwards by the French War Committee, a ruling which was not rescinded for about three months. Operation Wilfred was left to take place on its own on 5 April and was then postponed to 8 April, later parts of the plan being cancelled when news arrived that the German fleet had sailed. The British and French were able to agree that Operation Royal Marine could begin as soon as the German offensive in the west commenced. Prelude Plan The plan had been presented to the British Cabinet in November 1939 by Winston Churchill, as