Captain Sizemore was the bombardier of a B-26B Invader bomber with 13th Bomber Squadron, 3rd Bomb Group. On 28 July 1950, while attacking a column of enemy tanks near Chong Ju, his aircraft crashed into a mountain. His remains were recovered.

Sizemore was awarded the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal and the Republic of Korea War Service Medal.