Grumman is Roy Mustang's commanding officer and mentor at East City headquarters in Amestris. Grumman holds the rank of Lieutenant General, is a powerful ally and enjoys playing Chess.
Grumman also authorized the transfer of Mustang's subordinates (Riza Hawkeye, Vato Falman, Jean Havoc, Kain Fuery and Heymans Breda) from East City to Central City.
In the English dub of the first Fullmetal Alchemist anime series Grumman was not named and only called "General". He spoke in one episode (plus some cameos) and was voiced by Gordon Fox.
In the English dub of Fullmetal Alchemist: Brotherhood Grumman is voiced by Bill Flynn and since this adaption is more faithful to the original manga, Grumman is a recurring character.