Complex sentence: The group struck coastal defenses on D-Day, 6 June 1944, and bombed enemy positions in support of the breakthrough at St Lo in July and the offensive against Brest in August and September 1944.
Split into simpler sentences: The group struck coastal defenses on D-Day, 6 June 1944. Bombed enemy positions in support of the breakthrough at St Lo in July and the offensive against Brest in August and September 1944.