the technically sophisticated s4 was too complicated to interest the military and the manufacturer's billancourt factory was too small to be listed for a switch-over to war production. production seems to have been drastically scaled back, during the early years of the war, but sources are vague on the extent and nature of any manufacturing activity, which presumably was further inhibited by the british bombing of the plant on 3 march 1942. at the end of the war, however, it was single seater racing cars based on the chassis of the salmson s4-61 that in 1945 were supplied for the activities of the "union sportif automobile" which launched a competition driving school in 1945. the venture did not endure beyond 1946, but the salmson s4-61 was seen to have survived the war.