It became a full member of the Old Swiss Confederacy in 1353, and during the 15th century managed to significantly expand its sphere of influence, notably with the conquest of Aargau in 1415.
With the acquisition of Vaud in 1536, Bern became the most powerful city-republic north of the Alps, and one of the leading Protestant cities in early modern Switzerland.
[2] In the late medieval period, Berne was very strongly identified with its heraldic animal, which was used as an allegory of the military and feudal power of the canton within the Old Swiss Confederacy.
The Zähringer leaders, although with no actual duchy of their own, were styled dukes by decree of the German king and exercised imperial power south of the Rhine.
[5] During the second half of the 12th century, Berchtold V of Zähringen built a small castle at Nydegg on the eastern part of the peninsula to guard the Aare.
[4] The original city was built westward along the narrow peninsula, with three main longitudinal streets running east to west.
After the founder Berchtold V died heirless, Bern gained her town privileges and became an Imperial Free City in the Goldene Handfeste which is traditionally dated to 1218.
The Goldene Handfeste purports to be from Emperor Frederick II, but is now believed by most scholars to be a Bernese forgery from the middle of the 13th century.
As Bern continued to expand during the early 14th century, they came into conflict with the Burgundian and Habsburg supported feudal lords and the neighboring city of Fribourg.
Under Bernese control, the five valleys enjoyed extensive rights and far-reaching autonomy in the Bäuerten (farming cooperative municipalities) and Talverbänden (rural alpine communities).
The Evil League (Böser Bund) in 1445 fought against Bernese military service and taxes following the Old Zürich War,[9] in 1528 the Oberland rose up in resistance to the Protestant Reformation and in 1641 Thun revolted.
During the city's rapid growth in the 13th century, the older castle of Nydegg around which the early settlement was built, was demolished, the Aare slopes fortified and the layout of today's Old Town established.
Initially, the Zytglogge tower marked the western boundary of the city from 1191 until 1256, when the Käfigturm took over this role until 1345, which, in turn, was then succeeded by the Christoffelturm (located close to today's train station) until 1622.
During the time of the Thirty Years' War two new fortifications, the so-called big and small Schanze (entrenchment), were built to protect the whole area of the peninsula.
Despite the waves of pestilence that hit Europe in the 14th century, the city continued to grow mainly due to immigration from the surrounding countryside.
[4] As Bern was not situated at any of the major trading routes, agriculture quickly became of principal economic importance and remained so throughout Bernese history.
In the 14th century, as the importance of European commerce began to rise, numerous wealthy trading families emerged as the city's aristocracy.
They mainly turned to government and mercenary service in the 15th century, though, and trade stagnated as the city's autocratic rule over the countryside strengthened.
The latter included the Schultheiss (mayor) as chief executive and the holders of other public offices such as guild representatives, Stadtschreiber (city clerk), Seckelmeister (bursar) and Grossweibel (Grand Bailiff).
[11] In the Middle Ages, upwards mobility and access to public offices was relatively easy for successful traders and craftsmen, but Bernese society became ever more stratified and aristocratic as the power and wealth of the city grew.
In effect, public offices were now the exclusive prerogative of the gnädige Herren, the "merciful lords", as the small number of noble families now ruling Bern came to be called.