Early development
Tolls were collected from ships sailing on the River Rhine in Europe for one thousand years from around 800 AD to 1800 AD. During this time, various feudal lords (among them archbishops who held fiefs from the Holy Roman Emperor) collected tolls from passing cargo ships to bolster their finances.[citation needed] Only the Holy Roman Emperor could authorise the collection of such tolls. Allowing the nobility and Church to collect tolls from the busy traffic on the Rhine seems to have been an attractive alternative to other means of taxation and funding of government functions.[citation needed]
Iron chains were often stretched across the river to prevent passage without paying the toll, and strategic towers were built to facilitate this.[citation needed]
The Holy Roman Emperor and the various noblemen and archbishops who were authorised to levy tolls seem to have worked out an informal way[vague] of regulating this process.[citation needed] Among the decisions involved in managing the collection of tolls on the Rhine were how many toll stations to have, where they should be built, how high the tolls should be, and the advantages/disadvantages.[citation needed] While this decision process was made no less complex by being informal, common factors included the local power structure (archbishops and nobles being the most likely recipients of a charter to collect tolls), space between toll stations (authorized toll stations seem to have been at least five kilometres apart)[citation needed], and ability to be defended from attack (some castles through which tolls were collected were tactically useful until the French invaded in 1689 and levelled them).[citation needed] Tolls were standardized either in terms of an amount of silver coin allowed to be charged or an "in-kind" toll of cargo from the ship.
The men who came to be known as robber barons or robber knights (German: Raubritter) violated the structure under which tolls were collected on the Rhine either by charging higher tolls than the standard or by operating without authority from the Holy Roman Emperor altogether.
Writers of the period referred to these practices as "unjust tolls," and not only did the robber barons thereby violate the prerogatives of the Holy Roman Emperor, they also went outside of the society's behavioural norms, since merchants were bound both by law and religious custom to charge a "just price" for their wares.
Great Interregnum
During the period in the history of the Holy Roman Empire known as the Great Interregnum (1250–1273), when there was no Emperor, the number of tolling stations exploded in the absence of imperial authority. In addition, robber barons began to earn their opprobrium by robbing ships of their cargoes, stealing entire ships, and even kidnapping.
In response to this organized, military lawlessness, the "Rheinischer Bund," or Rhine League was formed by 100 Cities, and from several princes and prince-prelates (lords of the Church), all of whom held large stakes in the restoration of law and order to the Rhine.
Officially launched in 1254, the Rhine League wasted no time putting robber barons out of business by the simple expedient of taking and destroying their castles. In the next three years, four robber barons were targeted and between ten and twelve robber castles destroyed or inactivated.
The Rhine League was not only successful in suppressing illicit collection of tolls and river robbery, they also took action against other state aggression. For example, they are documented as having intervened to rescue a victim of abduction by the Baron of Rietberg.
The procedure pioneered by the Rhine League for dealing with robber barons – to besiege, capture and destroy their castles – survived long after the League self-destructed from political strife over the election of a new Emperor and military reversals against unusually strong robber barons.
When the Interregnum ended, the new king Rudolf of Habsburg applied the lessons learned by the Rhine League to the destruction of the highway robbers at Sooneck, torching their castles and hanging them. While robber barony never entirely ceased, especially during the Hundred Years' War, the excesses of their heyday during the Interregnum never recurred.