neighboring_county_or_viking_conquest_trigger

neighboring_county_or_viking_conquest_trigger = {
	OR = {
		trigger_if = {
			limit = {
				$CHARACTER$ = {
					can_use_viking_invasion_cbs_trigger = yes
				}
			}
			is_coastal_county = yes
			OR = {
				$CHARACTER$ = { is_ai = no }
				is_neighbor_to_realm = $CHARACTER$
				$CHARACTER$ = {
					NOT = {
						any_sub_realm_title = {
							tier = tier_county
							NOT = {
								is_connected_to = {
									target = $CHARACTER$.capital_province.county
								}
							}
						}
					}
				}
			}
		}
		trigger_else = {
			$CHARACTER$ = { is_ai = no }
		}
		any_neighboring_county = {
			holder = {
				target_is_same_character_or_above = $CHARACTER$
			}
		}
	}
}

As written in game/common/scripted_triggers/00_war_and_peace_triggers.txt.