add_attacker_bloc_members_on_declared_effect

add_attacker_bloc_members_on_declared_effect = {
	scope:attacker.house.house_confederation ?= {
		every_confederation_member_house = {
			every_house_member = {
				limit = {
					top_liege = scope:attacker.top_liege
					is_landed = yes
				}
				save_temporary_scope_as = bloc_member_temp
				scope:war = { add_attacker = scope:bloc_member_temp }
			}
		}
	}
}

As written in game/common/scripted_effects/10_dlc_tgp_house_bloc_scripted_effects.txt.