Ally

盟友

méngyǒu

(person, group, concept, etc., which is associated with another as a helper — see also auxiliary, supporter)

盟國 /盟国

méngguó

(person, group, state, etc., which is associated or united by treaty with another for a common (especially military or political) purpose)

結盟 /结盟

jiéméng

(to unite or form a connection between (people or things))