In 1618, the famous second defenestration of Prague provoked the Thirty Years' War, a particularly harsh period for Prague and Bohemia. Ferdinand II of Habsburg was deposed, and his place as King of Bohemia taken by Frederick V, Elector Palatine; however his army was crushed in the Battle of White Mountain (1620) not far from the city. Following this in 1621 was an execution of 27 Czech Protestant leaders (involved in the uprising) in Old Town Square and the exiling of many others. Prague was forcibly converted back to Roman Catholicism followed by the rest of Czech lands. The city suffered subsequently during the war under an attack by Electoral Saxony (1631) and during the Battle of Prague (1648). Prague began a steady decline which reduced the population from the 60,000 it had had in the years before the war to 20,000. In the second half of the 17th century, Prague's population began to grow again. Jews had been in Prague since the end of the 10th century and, by 1708, they accounted for about a quarter of Prague's population.