the foundational period of the Confederacy was at its peak, and the default view was to regard the reports of the late-15th-century chronists as essentially legendary. Since the late 1970s, systematic surveys of medieval castles in Central Switzerland have shown that a number of castles were indeed destroyed during the early 14th century, so that a possible historical nucleus of the Burgenbruch accounts may be granted, even though the destruction of these forts in itself was of limited military import and could not have resulted in a lasting political change. Expansion to the Acht Orte Subsequently, the three communities (their territories did not yet correspond to the areas of the modern-day cantons) followed a slow policy of expansion. Uri entered a pact with the previously Habsburg valley of Urseren in 1317. In 1332, the city of Lucerne, trying to achieve from the Habsburgs, joined the alliance. In 1351, these four communities were joined by the city of Zürich, where a strong citizenship had gained power following the installation of the (guild regulations) and the banning of the noble authorities in 1336. The city also sought support against the Habsburg city of Rapperswil, which had tried to overthrow mayor Rudolf Brun in Zürich in 1350. With the help of its new allies, Zürich was able to withstand the siege of duke Albert II of Austria, and the confederates even conquered the city of Zug and the valley of Glarus in 1352. They had to return both Glarus and Zug to the Habsburgs in the peace treaty of Regensburg in 1356; emperor Charles IV in return recognized the of Zürich and confirmed its status in spite of his having forbidden any confederations within the empire in his Golden Bull issued in January of that same year. The Eidgenossenschaft had signed "perpetual" pacts with both Glarus and Zug in 1352, and thus, even if these pacts apparently were disregarded only a few years later, this date is often considered the entry of these two cantons into the confederation despite their remaining under Habsburg rule for a few more years. In the west, the Vier Waldstätten had already formed an alliance with the city of Bern in 1323, and even sent a detachment to help the Bernese forces in their territorial expansion against the dukes of Savoy and the Habsburgs in the Battle of Laupen in 1339. In 1353, Bern entered an "eternal" alliance