The terms ‘Poland’ and ‘Poles’ begin to appear in written records of European history around the 10th century. The region that would become Poland was inhabited by several tribes, led by dux (dukes). The two biggest and most powerful tribes – the Polanie and the Wiślanie – brought the other tribes under their control. Eventually, the Wiślanie came under the rule of the first Polanie King to be mentioned in recorded history, Mieszko I. Mieszko converted Poland to Christianity, bringing the country into the fold of Western Christendom. In the 13th century, Poland became prosperous thanks to the development of salt, silver and gold mining industries. It was a vital part of Europe’s emerging trade networks, and settlers from Western Europe came to the region, attracted by the relative freedom. In the later 14th century, Jadwiga, Queen of Poland married Jogaila, the Grand Duke of Lithuania. The marriage linked the small kingdom with Lithuania, then a large and diverse country. Though Lithuania had been pagan, Jogaila accepted Roman Catholicism for himself and his country on his marriage. In 1568, the informal alliance was further formalised with the Union of Lublin, which provided for a jointly elected grand-duke and legislature, unique in Europe. The early 16th century is generally seen as Poland’s ‘golden age’, when arts and sciences flourished in the region. The nation developed a reputation for relative tolerance towards Jews, meaning that Poland long had Europe’s biggest Jewish population.