show_pow_release_message_effect

show_pow_release_message_effect = {
	if = {
		limit = {
			any_character_war = {
				primary_attacker = scope:attacker
				primary_defender = scope:defender
			}
		}
		every_character_war = {
			limit = {
				primary_attacker = scope:attacker
				primary_defender = scope:defender
			}
			save_scope_as = war
		}
		if = {
			limit = { prisoners_of_war_trigger = yes }
			custom_tooltip = release_pow_at_end_of_war
		}
	}
}

As written in game/common/scripted_effects/00_war_effects.txt.