There are sharply divided opinions of Pound's leadership. His greatest achievement was his successful campaign against German U-boat activity and the winning of the Battle of the Atlantic. Winston Churchill, the civilian head of the Navy (1939–40) and of all the forces as Prime Minister (1940–45) worked with him closely on naval strategies; he was dubbed "Churchill's anchor". He blocked Churchill's scheme of sending a battle fleet into the Baltic early in the war. However his judgment has been challenged regarding his micromanagement, the failed Norwegian Campaign in 1940, his dismissal of Admiral Dudley North in 1940, Japan's sinking of the "Repulse" and the "Prince of Wales" by air attack off Malaya in late 1941, and the failure in July 1942 to disperse Convoy PQ 17 under German attack.