<page_title> List of rulers of Brittany </page_title> <section_title> Breton War of Succession </section_title> <table> <cell> John (IV) of Montfort (Yann IV Moñforzh) May 1341-1345 <col_header> Name </col_header> </cell> </table>
John IV (Yann IV, John of Montfort) was Duke of Brittany.