Germany
An Age of Disorder
The 15th century was the heyday of the so-called robber barons, a term invented by the bourgeois merchants. The Germany nobility did indeed prey upon merchants. You should not picture them swooping down from mountain fortresses to loot mule trains and waggons, though such surely did occur; the reailty was both more prosaic and more disruptive. The barons set up tolls—to use their roads, their bridges, their canals, even the rivers. They also ran protection rackets, charging mercahnts so nothing "bad" would happen to them.
Understandably, merchants did not much care for these added expenses and risks. If the cities tried to retaliate, that's when the mountain fortresses came into play, for the barons could simply retreat there and wait for the enemy forces to run out of supplies and money.
In England or France, the monarch eventually proved the only source of real peace, but in Germany the imperial courts were toothless and imperial decrees could not infringe on princely privileges. So the cities themselves formed leagues, to join their resources and bring superior force against their baronial rivals. The best-known example is the Swabian League, formed in 1488.
This league was not like the earlier Rhenish League because it included knights and biships and even some barons. It was also unlike the Hanseatic League in that its aims were more political than mercantile. In the absence of a strong central authority, an absence the Germans had worked hard to get, the Swabian League represents one attempt to find some other way to establish and preserve public order.
It succeeded only marginally and only in southern Germany. Elsewhere, cities were as much the source of strife as were the barons. In Brandenburg, in Saxony, in the Rhine Valley, it was the prince who played the role of the English or French king, bringing barons and cities alike to heel.
All this was played out with little or no imperial influence. Frederick simply lacked the legal and financial tools necessary to the task.