Con Colbert attained the rank of captain in Éamonn Ceannt’s 4th Battalion of the Dublin Brigade. He became heavily involved in training and developing his company. Although small in stature, being just over five feet tall, he had considerable presence and was a charismatic trainer and leader.
During the Easter Rising, Colbert and his company were assigned to Watkins’s brewery to the east of the South Dublin Union, which was held by Ceannt and the main body of the 4th Battalion. Once the brewery proved to have no strategic significance, Colbert and his company joined Séamus Murphy at Jameson’s Distillery in Marrowbone Lane, closer to the South Dublin Union. As this position was by-passed by the cordon of British troops that gradually encircled the city centre, the garrison did little fighting, eventually surrendering on Sunday, 30 April 1916.
Con Colbert was tried by court-martial and sentenced to death. He was executed on 8 May 1916. He was unmarried.