The British launched Operation Dynamo, which evacuated the encircled British, French and Belgian troops from the northern pocket in Belgium and Pas-de-Calais, beginning on 26 May. About 28,000 men were evacuated on the first day. The French First Army – the bulk of which remained in Lille – fought the Siege of Lille owing to Weygand's failure to pull it back along with other French forces to the coast. The 50,000 men involved capitulated on 31 May. While the First Army was mounting its sacrificial defence at Lille, it drew German forces away from Dunkirk, allowing 70,000 Allied soldiers to escape. Total Allied evacuation stood at 165,000 on 31 May. The Allied position was complicated by Belgian King Leopold III's surrender on 27 May, which was postponed until 28 May. The gap left by the Belgian Army stretched from Ypres to Dixmude. A collapse was averted at the Battle of Dunkirk and 139,732 British and 139,097 French soldiers were evacuated by sea across the English Channel in Operation Dynamo. Between 31 May and 4 June, another 20,000 British and 98,000 French were saved; about 30,000 to 40,000 French soldiers of the rearguard remained to be captured. The total evacuated was 338,226, including 199,226 British and 139,000 French.