Much of the medieval period was a time of power struggles between competing dynasties such as the House of Savoy, the Visconti in northern Italy and the House of Habsburg in Austria and Slovenia. In 1291 to protect themselves from incursions by the Habsburgs, four cantons in the middle of Switzerland drew up a charter that is considered to be a declaration of independence from neighboring kingdoms. After a series of battles fought in the 13th, 14th and 15th centuries, more cantons joined the confederacy and by the 16th century Switzerland was well-established as a separate state.