By 26 May the BEF was cut off and the decision was made to evacuate it through Dunkirk (Operation Dynamo), with II Corps acting as flank guard against the German penetration where the Belgian Army had surrendered. The last of the BEF who could enter the Dunkirk bridgehead had done so by 29 May and the evacuation progressed: III Corps went first, followed by II Corps after handing over responsibility for the eastern flank to the rearguards of I Corps. Most of II Corps was evacuated on the night of 31 May/1 June.