In layman's terms, it is a person whose troops cooperate with their own troops or unite themselves.

A friendly army refers to an army that does not belong to the same high command, has the same operational goal as its own, and cooperates with it. Such as the national and communist armies during the Anti-Japanese War, Chinese people's Volunteer Army and the Korean People's Army during the War to Resist US Aggression and Aid Korea.

1. Not belonging to the same high command;

Second, there is a common operational goal;

Third, we can cooperate.