Complex sentence: Marks returned to operations in March 1941 and served with 58 Squadron, where he was engaged in attacks against Brest, where the German warships "Scharnhorst" and "Gneisenau" were in dock, joined in June by the "Prinz Eugen".
Split into simpler sentences: Marks returned to operations in March 1941 and served with 58 Squadron, where he was engaged in attacks against Brest. There the German warships "Scharnhorst" and "Gneisenau" were in dock, joined in June by the "Prinz Eugen".