William Bill Guarnere is the youngest in a family of 10 children from the southern suburbs of Philadelphia in the United States.

He joined the Citizen Military Training Corps with the encouragement of his mother, who sees the army as a chance for his son to eat, dress, and be away from the city.

Guarnere William spent three years at the CMTC, but the program is canceled when the war began. Very interested and fascinated by the paratroopers, he volunteered in 1942 and began his basic at Toccoa, Georgia.

On 5 June 1944 in England, just before leaving for Normandy, he learned that his brother was killed in combat in Italy at Monte Cassino.

Il est rapidement surnommé "Wild Bill" ("Bill le Sauvage") à cause de sa grande combativité face aux soldats allemands pendant la guerre, il perd une jambe au combat à Bastogne, lors d'un barrage d'artillerie. He was quickly nicknamed "Wild Bill" because of his great fighting spirit against German soldiers during the war. He lost a leg in combat in Bastogne during an artillery barrage.

Bill Guarnere wrote his war memoirs in the book Brothers in Battle, Best of Friends.