On 18 December 1939, 24 Wellingtons of No. 9, No. 37 and No. 149 Squadrons participated in the Battle of the Heligoland Bight against the German fleet and naval bases in both the Schillig Roads and Wilhelmshaven. The Wellingtons were unable to deploy their bombs as all vessels were in harbour, thus restrictions on endangering civilians prevented their engagement. Having been alerted by radar, "Luftwaffe" fighter aircraft intercepted the incoming bombers near to Heligoland and continuously attacked the formation much of the way home. In total, 12 of the bombers were destroyed and a further three were badly damaged. Defensive fire from the turrets downed four aircraft.