the Union of Arras was concluded with Arras on January 6th 1579 between the Artois, the Cambrésis, the Comté of Hainaut and the Romance Flanders (except for the Tournaisis), under the impulse of Alessandro Farnese. The three countries worried about the policy of the calvinists in the towns of Flanders and in the remainder of the Netherlands. Violence against the catholic priests and the churches and the convents contravened the agreements made at the time of the Pacification of Ghent.

Also the provinces of the South decided to approach in order to defend the catholic faith and honesty with the king. A few weeks later, the Union of Utrecht will be proclaimed by a series of others Spanish Netherlands, being thus opposed to the Union Atrecht (Arras in Dutch). The Union of Arras of sound with dimensions was followed of the Treaty of Arras, on May 17th, per which the provinces of this union were reconciled with the king Philippe II of Spain.