加盟【かめい】
joining (an association, agreement, etc.), participation, affiliation, accession
同盟【どうめい】
alliance, union, league
連盟【れんめい】
league, federation, union, alliance
盟主【めいしゅ】
leader (of an alliance), leading power
盟約【めいやく】
oath, pledge, pact, covenant, alliance