Meanwhile, Army Group A had cut the BEF's lines of communication into France and driven it back towards the coast at Dunkirk, cutting off the British troops at Calais and Boulogne from the main force. When planning the evacuation from Dunkirk (Operation Dynamo), the BEF's commanders decided that Calais and Boulogne should still be held as supply points for further fighting or possible exit points for a final withdrawal.