Membership: Membership refers to being an official part of a group or organization. Joining the League of Nations would involve gaining membership in this international organization.
Affiliation: Affiliation means formally associating oneself with a particular group or entity. The decision to join the League of Nations would result in affiliating with this global body.
Enrollment: Enrollment is the process of officially registering as a member or participant. Joining the League of Nations would require enrolling and becoming an active participant in its activities.