Complex sentence: He was commanding HMS "D5" at the outbreak of World War 1 in August 1914, and his time in charge of that submarine, prior to moving to Q-ships in January 1915, was not without incident.
Split into simpler sentences: He was commanding HMS "D5" at the outbreak of World War 1 in August 1914. His time in charge of that submarine, prior to moving to Q-ships in January 1915, was not without incident.