How did the Union of Arras support Spanish rule in the southern Netherlands?

The Union of Arras, formed on January 6, 1579, was a pivotal agreement that supported Spanish rule by reconciling the conservative, largely Roman Catholic southern provinces—specifically Artois, Hainaut, and the town of Douay—with King Philip II of Spain.12

By formalizing their loyalty to the Spanish crown and committing to the preservation of the Roman Catholic religion, these provinces effectively broke away from the broader resistance movement led by William of Orange. This political shift provided the Spanish governor-general, Alessandro Farnese, with a crucial strategic advantage. It allowed him to isolate the rebellious, predominantly Protestant northern provinces—which subsequently formed the Union of Utrecht—and focus his military and diplomatic efforts on restoring Spanish authority across the southern Netherlands.1324

Ultimately, the Union of Arras served as the foundation for the consolidation of the Catholic southern provinces under Spanish control, a region that would later become modern-day Belgium.24