At the end of 1943, the squadron had completed the second largest number of successful operations of units within No. 1 Group Bomber Command and had the lowest 'loss' rate. On the night of 16/17 December 1943, the squadron received orders to attack Berlin. The raid became known as 'Black Thursday' as Bomber Command lost 25 aircraft on the raid and 28 in crashes at fog-shrouded airfields. That night, 100 Squadron lost their commanding officer, David Holford, who crashed landed approaching RAF Grimsby. On the night of 5 June 1944, the squadron bombed heavy gun batteries in support of the D-Day invasion.