The major problem of the Atlantic Fleet were German U-boats, which threatened allied supply convoys and sunk more than 5.7 million tons of merchant shipping. Bellinger established Anti-Submarine Warfare Detachment that taught pilots the latest Anti-Submarine Warfare tactics, tested new devices, and equipped planes with a microwave search radar. He also created Combat Information Centers and Fighter Director Officer Teams aboard his carriers. Bellinger was promoted to the rank of Vice admiral on October 5, 1943.
