In his teenage years, Colalillo attended Denfeld High School but dropped out before graduating in order to help support his family by working at a local bakery after the passing of his mother.

Colalillo encouraged his comrades to follow him into enemy fire, manned an exposed machine gun, and helped a wounded soldier back to friendly lines.

Citation: The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Private Michael "Mike" Colalillo, United States Army, for conspicuous gallantry and intrepidity in action above and beyond the call of duty on 7 April 1945, while serving with Company C, 1st Battalion, 398th Infantry, 100th Infantry Division.

Maintaining his extremely dangerous post as the tank forged ahead, he blasted three more positions, destroyed another machine gun emplacement and silenced all resistance in his area, killing at least three and wounding an undetermined number of riflemen as they fled.

When our armored forces exhausted their ammunition and the order to withdraw was given, he remained behind to help a seriously wounded comrade over several hundred yards of open terrain rocked by an intense enemy artillery and mortar barrage.