The drive up the Belgian coast in June-July of 1917, for which the Canadians provided diversionary trench raids at the Souchez River, was undertaken for a number of reasons. One hope was to combat the threat posed by the Zeppelin airships and Gotha bombers. British forces fighting up the coast would require the Germans to depart from airfields further from England, as well as to fly over more British-controlled territory. This would shorten the loiter time available to the German flights once over English skies, reducing their effectiveness, while also increasing the chances of British ground forces shooting down aircraft whilst flying overhead on the coast.
The threats from air attack had increased with the continuing development of Gotha bombers, used in addition to the Zeppelin airships. On May 25, 1917, a daylight raid of 21 Gotha bombers struck in the Folkestone-Shorncliffe region, creating approximately 300 casualties. Of these, 17 fatalities and 93 wounded were Canadian soldiers, training and awaiting transfer to the front. On 13 June 1917, London suffered its first daylight bombing raid, with 162 persons killed and 432 injured.