'Maple' (ii) was an Allied naval and air operation to clear German minefields and lay Allied minefields in support of the 'Neptune' (iii) and 'Overlord' invasion of north-western France (6 June 1944).
The operation’s objectives were to impede the movement of German light warships stationed inside the Channel; to impede the entry into the Channel by German naval forces situated in the Atlantic and North Sea; to force German naval forces moving toward the 'Neptune' (iii) area to follow a course to seaward of the extreme range of their own shore batteries and shore-based fighter cover in order that Allied surfaces forces would be free to intercept their progress; and to disrupt German shipping generally during the critical period, in order to reduce seaborne movement of reinforcements and supplies toward the battle area.
The mines were laid by ships and aircraft, including the cruiser minelayer Apollo, coastal minelayer Plover, the vessels of the 10th, 50th, 51st and 52nd Mine-Laying Flotillas, and the motor torpedo boats of the 9th, 13th, 14th, 21st, 22nd and 64th Motor Torpedo Boat Flotillas. In addition, mines were laid from the air by Avro Lancaster, Handley Page Halifax and Short Stirling heavy bombers of Nos 1, 3, 4, 5 and 6 Groups of Air Chief Marshal Sir Arthur Harris’s RAF Bomber Command.
With the exception of the field laid in the Straits of Dover and an area mined by aircraft to the north of the Frisian islands group, all the minefields were offensive in character. The two semi-defensive minefields off Dover and the Frisian islands were intended primarily to counter any movement of German heavy warships from the east. In April and May 1944, some of the mines laid were timed to become effective at various dates so as to escape being swept before the invasion of France.
During 'Maple' (ii), some 6,850 mines were laid. Of these, 42% were laid by naval forces in 66 operations and 58% were laid by aircraft in 1,800 sorties. These operations made an effective contribution to the general immunity from surface and U-boat attack enjoyed by the assault forces.
Conversely, a considerable number of casualties were inflicted on the Germans, and their minesweeping organisation was stretched to the limit and indeed beyond. Minefields in the vicinity of Ushant and off the Brittany coast had the desired effect of driving U-boats into open water, where they could be tackled more effectively by the Allied anti-submarine forces. The linked 'Bravado' special operation in the Kiel Canal resulted in a complete dislocation of the German organisation at an important moment. The entire operation cost the Allies just one motor torpedo boat and minelaying aircraft. 'Maple' (ii) was linked in overall terms with the 'Bravado' operation off Kiel, and the two operations were regarded as very successful.