He joined Breiz Atao in 1919 and became president of Unvaniez Yaouankiz Vreiz ("Youth Union of Brittany") in 1922. Together with Roparz Hemon, he created the literary magazine Gwalarn (1925), and was included in the Breton delegation to the First Pan-Celtic Congress in Dublin (alongside François Jaffrennou, Morvan Marchal, and Yves Le Drézen).
He joined Breiz Atao in 1919 and became leader of Unvaniez Yaouankiz Vreiz ("Youth Union of Brittany") in 1922. Along with Roparz Hemon, he founded the literary magazine Gwalarn (1925), and was included in the Breton delegation to the First Pan-Celtic Congress in Dublin (alongside François Jaffrennou, Morvan Marchal, and Yves Le Drézen).