The coastal Frisian Kingdom remained Germanic pagan but were eventually conquered by Charles Martel and incorporated into the Catholic Frankish Kingdom after the Battle of the Boarn in 734. The Northern parts of the Netherlands were converted as part of the Anglo-Saxon mission as Catholic Christians from the various kingdoms of Anglo-Saxon England moved to the Continent, such as St. Willibrord, the Apostle of the Frisians and St. Boniface, who was martyred in Friesland. Both were active in the eighth century, having great impact on the conversion of the country. The areas in the Low Countries which would eventually become part of the modern Netherlands were part of Middle Francia and then Lotharingia, before eventually becoming part of the Holy Roman Empire of the German Nation as part of the Burgundian Netherlands. Originally under the House of Valois-Burgundy by the end of the 15th century it was part of the Habsburg Netherlands as part of a vast Catholic Habsburg Empire dominated by the Kingdom of Spain.