The team began playing in the All-America Football Conference in 1946. They were members of such a league for 4 years before joining the National Football league in 1950. During their time in the 'AAFC' the team found tremendous success. They were league champions four times in their stay, including a 15-0 undefeated season in 1948. The Browns truly were the most dominant team that the AAFC ever saw during the life of the league.