Map of the Netherlands in 1579
The Union of Arras was a treaty signed on 6 January 1579 by Spain's provinces in the southern Netherlands (now in the Flanders region of France and Belgium). The Union of Arras stated that Catholicism was the only legal religion in the region, that society should be restored to what it was before the Dutch Revolt, and that no more foreign troops should be garrisoned in the Netherlands. The northern states signed the Union of Utrecht in opposition to the Catholics of the south.