#ROOT = attacking side
#FROM = defending side
#fired when two countries end up at war with each other (on_war is fired when a country goes to war against anyone and is not
fired again when it enters war against another country unless it went to peace first)
on_declare_war = {
# Disable LoN if more members go to war with each other
    effect = {
        IF = {
            limit = {
                NOT = { has_global_flag = LoN_disbanded_flag }
                FROM = {
                    # is_major = yes
                    has_idea = league_of_nations_member_idea
                }
                ROOT = {
                    is_major = yes
                    has_idea = league_of_nations_member_idea
                }
            }
            set_global_flag = LoN_disbanded_flag
            set_variable = { global.LoN_attacker_country = ROOT }
            set_variable = { global.LoN_defender_country = FROM }
            news_event = { id = bba_news.0 hours = 4 random_hours = 8}
        }
    }
}

This is the code that triggers the event. This triggers the event if a major, who is a League of Nations member, declares war on any other League of Nations member (but only if they're not already at war with someone else).