The War of the Reunions (1683-1684) was a small conflict between Louis XIV's France and Spain and her allies. It was part of Louis' long lasting attempts to take portions of the Spanish Netherlands. As such it is a direct sequel to the War of Devolution and the Dutch War.
The treaties ending those two wars, as well as the Treaty of Westphalia of 1648 had ceded a number of towns to France. By tradition when a town changed hands so did the rural areas around it that provided it with its food and other such supplies. The borders of these dependent regions were ill defined. Thus Louis and his court, beginning in 1670, introduced several Courts of Reunion that would investigate whether France had been granted all the territory it had been owed.
Not surprisingly these French courts ruled that a number of areas were owed to France. These territories generally consisted of small towns of unclear ownership, and for the most part Louis' annexations went unopposed. The territory seized mainly came from the Spanish Netherlands and the western parts of the Holy Roman Empire, especially Alsace.
However, this left large rural lands in Louis' control unprotected by major garrison towns. The two most important of these were Strasbourg and Luxembourg City. Strasbourg dominated Louis' newly annexed territories in Alsace, just as the great fortress of Luxembourg dominated the regions Louis had annexed from the Spanish Netherlands. In 1681 Strasbourg was annexed after Louis surrounded the city with overwhelming force.
Luxembourg refused to fall, however, and war broke out between the Spanish forces in the Netherlands, backed by the Holy Roman Empire, and France in the winter of 1683. As in previous wars Louis easily defeated the Spanish forces, seizing a number of towns.
However, that same year the Ottoman Empire launched its greatest offensive ever against the eastern flank of the Empire, beginning the War of the Holy League. While Louis refused to send aid to the Empire and had even secretly encouraged the Ottomans he did feel it would be unseemly for him to continue fighting the Empire on its western border. Thus Louis agreed to the Truce of Ratisbon, guaranteeing twenty years of peace between France and the Empire and asking the King of England to arbitrate the disputed border claims.
This peace would not last leading to the Nine Years War five years later.