Through advocacy by
Eric Kennington to the
War Artists' Advisory Committee, Gross was offered, and accepted, the role of an official war artist, and produced etchings and oil and watercolour paintings of English coastal defences and troop training. In 1941, with a temporary commission of captain, Gross was attached to the
9th Army and painted within the Egyptian, Syrian, Palestinian, Kurdistan, Lebanese, and Mesopotamian theatres of war, sometimes accompanied by other war artists
Edward Ardizzone and
Edward Bawden, and later documenting the
8th Army's
North African Campaign. From 1943 he transferred to India and Burma to witness the front line battle against the Japanese; these works were the subject of a one-man exhibition at the
National Gallery when he returned to England. Gross accompanied the
D-Day invasion of Northern France, wading ashore near
Arromanches at 2pm on D-Day. He sketched the
beachhead landings and spent the night in a slit trench on the beach before moving inland the next day. Gross recorded the devastation of
Bayeux and
Caen, and followed the Allied armies to Paris and then into Germany. He witnessed the meeting of American and Russian forces at the River Elbe on
25 April 1945. Gross was, at the time, one of the many war artists who painted a portrait of
General Montgomery. ==Post war==