What caused the Saxon rebellion against Henry IV in 1073?

The Saxon rebellion of 1073 was primarily caused by the aggressive policies of Henry IV aimed at consolidating royal power and recovering crown lands in Saxony.

Key factors contributing to the uprising included:

• Territorial Encroachment: Henry sought to reclaim royal rights and lands that had been lost or appropriated by the nobility during his minority. He established a fortified royal territory stretching from the Harz Mountains to the Thuringian Forest, which displaced local interests.12
• Use of Ministeriales: To bypass the influence of the traditional lay princes, Henry relied on ministeriales—unfree knights and officials—to administer these lands and garrison his new strongholds. The high-handed and severe measures of these foreign officials deeply alienated the local population.13
• Peasant Discontent: The free peasantry of Eastphalia, who were forced to perform heavy statute labor to construct the king's fortresses, joined the Saxon nobles and prelates in revolt against the regime of Henry’s Frankish and Swabian officials.13