In pursuit of his military career, with his West Country cousins, Godolphins, Carews, Killigrews, Champernownes, Basets, etc., Grenville fought against the Turks in Hungary for the Holy Roman Emperor, Maximilian in 1566. After petitioning Elizabeth I in 1565 to leave England for service abroad to a foreign prince, Grenville and his West Country cousins paid for and recruited a troop of West Countrymen to accompany them.