27 crosses in the pavement of the Old Town Square in Prague mark the spot where 27 martyrs were beheaded following the Battle of the White Mountain in 1620. The battle was part of the Thirty Years War (1618 - 1648), a struggle for control of central Europe between countries that professed either Catholic or Protestant beliefs. The Battle of the White Mountain marked the end of the Bohemian part of the Thirty Years War and the religious revolution begun by Jan Hus at the beginning of the 15th century. It and was followed by a strong reassertion of Catholicism in Czech lands.
Jan Hus (or John Huss, 1369 - 1415) was a Czech priest, philosopher and one of the first church reformers. Hus attacked moral failings among the clergy and promoted some of the teachings of John Wycliffe (1331 - 1384), an English reformere who had been burned at the stake in 1384. Hus was excommunicated for his views in 1410 and burned at the stake as a heretic in Konstanz on 6 July 1415.