[terry]

It was normal for players to play both offense and defense until the 1940s. In 1941, the NCAA changed the rules to allow unlimited substitution. That made it feasible to use separate squads for both offense and defense. After the war, some teams started to use separate offensive and defensive squads. Even on those two-platoon teams, some players continued to play both ways. In 1954, the NCAA tightened up the substitution rules, essentially requiring most players to play both ways. The rules changed again after the 1964 season, again allowing separate offensive and defensive squads.

[terry]

It was normal for players to play both offense and defense until the 1940s. In 1941, the NCAA changed the rules to allow unlimited substitution. That made it feasible to use separate squads for both offense and defense. After the war, some teams started to use separate offensive and defensive squads. Even on those two-platoon teams, some players continued to play both ways. In 1954, the NCAA tightened up the substitution rules, essentially requiring most players to play both ways. The rules changed again after the 1964 season, again allowing separate offensive and defensive squads.