British logistics played a key role in the success of Operation Overlord, the Allied invasion of France in June 1944. The objective of the campaign was to secure a lodgement on the mainland of Europe for further operations. The Allies had to land sufficient forces to overcome the initial opposition and build it up faster than the Germans could respond. Planning for this operation had begun in 1942. The Anglo-Canadian force, the 21st Army Group, consisted of the British Second Army and Canadian First Army. Between them they had six armoured divisions (including the Polish 1st Armoured Division), ten infantry divisions, two airborne divisions, nine independent armoured brigades and two commando brigades. Logistical units included six supply unit headquarters, 25 Base Supply Depots (BSDs), 83