At the start of the Second World War, French was Admiral Commanding, Orkneys and Shetlands (ACOS). On 14 October 1939, the anchorage of Scapa Flow was infiltrated by the German submarine U-47, which sank the battleship HMS Royal Oak with the loss of 833 lives. The official report into the disaster cast blame for the weak defences at Scapa on French. Despite having earlier warned of the dangers of attack, and offering to bring a small boat or submarine into the anchorage to prove his point, French was forced to retire from active service, and was posted to Washington as an administrative and maintenance representative, serving there until 1944.[4]