In the 1667-1668
War of Devolution, France captured most of the
Spanish Netherlands and the Spanish province of
Franche-Comté but many of their gains were relinquished by the
Treaty of Aix-la-Chapelle, agreed with the
Triple Alliance of the
Dutch Republic, England and
Sweden. To split the Alliance, ]Louis XIV paid Sweden to remain neutral, while signing an alliance with England against the Dutch in the 1670
Treaty of Dover. France invaded the Dutch Republic in May 1672 at the start of the
Franco-Dutch War and initially seemed to have won an overwhelming victory. However, the Dutch position stabilised, while concern at French gains brought support from
Frederick William of Brandenburg-Prussia,
Emperor Leopold and
Charles II of Spain. France retained the Dutch stronghold of
Maastricht, but withdrew from the Netherlands in 1673, additional fronts opening in the
Rhineland and the Spanish
Pyrenees. The French position weakened in early 1674, when
Denmark-Norway joined the Alliance in January, followed by the February
Treaty of Westminster making peace between England and the Dutch Republic. An effective Allied response in Flanders was hampered by power struggles in
Madrid, while Spanish control over the Spanish Netherlands was by now largely nominal. Although peace talks were ongoing, Louis followed his normal policy of taking the offensive, then negotiating from strength; the French used the 1676 campaign season to capture
Condé-sur-l'Escaut,
Bouchain,
Maubeuge and
Bavay. This cut off
Valenciennes and
Cambrai, while French cavalry prevented movement of troops and devastated areas around the towns.
Marshall Schomberg, French commander in Flanders, had proposed taking Cambrai in August, but was ordered to relieve
Maastricht, then under siege by the Dutch. The plan for 1677 was to take Valenciennes, Cambrai and Saint-Omer, completing the French
frontière de fer or "iron border;" Louis calculated this would leave the Dutch little reason to continue. Supply depots were assembled along the border with the Spanish Netherlands, enabling operations to begin in February, a month earlier than usual. In late February, a detachment of 12,000 moved against Saint Omer, while the main army of 35,000 under
Luxembourg besieged Valenciennes. ==The siege==