Treaties of Nijmegen
Although the Dutch signed the Treaties of Nijmegen on 10 August 1678, a joint Spanish-Dutch army fought at Saint-Denis on 13th. Having secured Mons, Spain made peace on 19 September, ceding Saint-Omer, Cassel, Aire, Ypres, Cambrai, Valenciennes and Maubeuge to France. Ypres was later returned but this fixed France's northern frontier close to where it remains today.