Retired Army Col. Wendell Blanchard, 74, who served in the cavalry and later played a key role in defeating the Germans in the Battle of the Bulge, died Thursday at Walter Reed Hospital after a long illness.

During the Battle of the Bulge, the last major German offensive on the Western Front in World War II, Col. Blanchard headed combat command R of the 4th Armored Division of Gen. George S. Patton's 3d Army.

In a celebrated maneuver, the division wheeled north on Dec. 18, 1944, two days after the German offensive began, and raced into Belgium, covering 150 miles in 19 hours.

On Christmas Day, the tanks of Col. Blanchard's command broke into the besieged city of Bastogne, to relieve the beleaguered troops of the 101st Airborne.

The relief of Bastogne helped seal the doom of the German offensive.

Col. Blanchard was born in East Pepperell, Mass., and graduated from the Military Academy at West Point in 1924.

After receiving his commission as a second lieutenant, he served in horse cavalry units in the United States and in the Philippine Islands. In 1935, he was assigned to the fledgling 1st Mechanized Cavalry, at Ft. Knox. Ky., serving as one of the first tank troop commanders. He joined Gen. Patton at Ft. Benning, Ga., in 1940, in activating the 2d Armored Division. In 1942, he took part in the division's combat landing in North Africa.

In Africa, he was promoted to colonel and became commander of the 67th Armored Regiment. Later, as deputy chief of staff of the 4th Armored, he was responsible for the division's supply and logistics during Patton's dash across France.

Subsequently, as head of combat command R he led the unit in fighting at Luneville and won the French Legion of Honor and Croix de Guerre. In the relief of Bastogne he was wounded and receive the Purple Heart.

After the war, he taught strategic intelligence at the Command and General Staff School at Ft. Leavenworth, Kan., and was a military attache in Brussels. He then held a high ranking post in intelligence at Army headquarters here.

Following his retirement from the Army in 1954, he worked for the foreign area studies division at American University, collaborating in, editing and supervising preparation of more than 60 foreign area handbooks for the Army.He retired as FAS director in 1968.

In addition to his wife, Frances, of the home in Chevy Chase, survivors include a son, Bruce, of Oxon Hill, two daughters, Lydia von der Muhil of Santa Cruz, Calif., and Carol Gochenour of West Dummerston, Vt., and seven grandchildren.