In the early 13th century Baldwin of Luxembourg, Archbishop and Elector of Trier and uncle to the Emperor Karl IV, extended and consolidated his territory towards Koblenz. The threatened lords and knights endeavoured to hinder his ambitions. Together with the neighbouring castles of Waldeck, Schöneck and Ehrenburg, the knights of Eltz formed a protective alliance – a "Schutz- und Trutzbündnis" – to stop him. In 1331 Baldwin led a counter attack against this alliance.
With the help of the first recorded cannon attack north of the Alps, Baldwin attempted unsuccessfully to storm the western side of Eltz castle.The oldest cannon bolts in the world tell the story of this remarkable military event and they can be seen in the Armoury. After this Baldwin built a siege castle opposite Eltz castle - The Trutz- or Baldeneltz (spite castle). From here the castle was bombarded with stone balls from catapults, a normal strategy of war in those times. It is not known how long the siege lasted, but at least two years and possibly up to four. Proof of this harsh conflict lie in the stone balls in the inner courtyard. Whether the site was captured by storm or following a long siege remains unknown; it is also possible that the feud was brought to a negotiated settlement. However, there is no doubt that, in 1336, the Eltz feud came to an end.