Siege operations began on 28 February, supervised by French military engineer Sébastien Le Prestre de Vauban, and the town surrendered on 17 March; Spain formally ceded it to France under the August 1678 Treaty of Nijmegen.

[7] Peace talks had begun at Nijmegen in 1676 but Louis' policy was to take the offensive before agreeing terms and negotiate from strength; the French quickly captured Condé-sur-l'Escaut, Bouchain, Maubeuge and Bavay.

[9] The plan for 1677 was to take Valenciennes, Cambrai and Saint-Omer; this would complete the French frontière de fer or "iron border," which Louis calculated would leave the Dutch little reason to continue.

Over the winter, Marquis de Louvois assembled supply depots along the border with the Spanish Netherlands, allowing the campaign to open in February, a month earlier than usual.

For propaganda purposes, Louis often appeared at major sieges and joined Luxembourg at Valenciennes, along with other subordinate commanders including his brother, Philippe of Orléans, d'Humières and La Feuillade.

At 9:00 a.m. on 17 March, the attackers formed two columns and stormed the walls; they achieved complete surprise and quickly over-ran the defenders, capturing a bridge over the Rhonelle that controlled access to the main city.

Both sides wanted to minimise the damage that would follow an assault, since Louis intended to annex it to France, while the conventions of siege warfare shielded a town from being sacked if the defenders yielded once 'a practicable breach' had been made.

The agreement ensured Spain retained Mons and on 19 September, they signed their own treaty with France, ceding Saint-Omer, Cassel, Aire, Ypres, Cambrai, Valenciennes and Maubeuge.

With the exception of Ypres, returned to Spain in 1697, this fixed France's northern frontier close to where it remains today but the Treaties of Nijmegen proved the highpoint of French expansion under Louis XIV.