Rear. Adm. Allen P. Mullinnix, 79, who won the Navy Cross while commanding a cruiser during the invasion of Iwo Jima in World War II, died Wednesday after being stricken by a sudden illness at his home in Washington.

Adm. Mullinnix was born in Attica, Ind., and grew up there. He graduated from the Naval Academy at Amnapolis in 1919, and earned a master's degree at Yale University in 1926. Apart from studying, his naval assignments befor World War II included assisting in the formation of amphibious forces.

In the war, he took part in the landings in North Africa. In 1944, he assumed command of the U.S.S. Pensacola, a cruiser, and participated in many campaigns in the Pacific, including the Aleutian Islands and Saipan.

In May, 1945, the Pensacola was among the warships supporting the Marine Corps landing on the island of Iwo Jima, one of the most difficult actions of the war. The Pensacola was struck six times by Japanese shore batteries. Adm. Mullinnix, then a captain, ordered emergency repairs to be made, returned his ship to its battle station, and destroyed the Japanese guns.

For this action he received the Navy Cross. His other military decorations included the Legion of Merit.

Adm. Mullinnix retired from the Navy in 1947. He earned a law degree from George Washington University in 1950, and practiced law briefly before retiring a second time.

Survivors include his wife, Helen Smith Mullinnix, of the home in Washington; a sister, Kathryne E., of Baton Rouge, La.; two stepsons, Gordon B. Hurlbut, of Tonganoxie, Kan., and John Henry Hurlbut, of Jupiter, Fla., and six step-grandchildren.