The siege of Mons, 15 March – 10 April 1691, was a major operation fought during the Nine Years' War, and was the main French objective for the 1691 campaign in the Spanish Netherlands.

In July Luxembourg fought and won his tactical masterpiece at the Battle of Fleurus, nullifying any Allied hopes of invading France, whilst at sea, Admiral Tourville defeated an Anglo-Dutch fleet off Beachy Head.

[6] Louvois engineered the considerable preparations for the siege throughout the preceding winter: stores were filled with supplies in Namur, Philippeville, Dinant and Givet, and no less than 21,000 labourers were gathered for the construction of the lines of circumvallation.

[9] The French now prepared for the rest of the 1691 campaign season with the creation of five large armies bound for five major fronts: Flanders, the Moselle, the Rhine, Piedmont, and Roussillon.

[10] Louis’ personal military advisor and expert in the art of war, the Marquis de Chamlay, argued that these victories should be followed by a field battle that would destroy the Allied army and force a conclusion to the conflict.

After William left his troops in the command of the Prince of Waldeck, Luxembourg's cavalry routed part of the Allied army at Leuze on 18 September, before all combatants returned to winter quarters.