History of Strasbourg remained neutral during the Thirty Years' War (1618-1648), and retained its status as a Free Imperial City. However, the city was later annexed by Louis XIV of France to extend the borders of his kingdom. Louis' advisors believed that, as long as Strasbourg remained independent, it would endanger the King's newly annexed territories in Alsace, and, that to defend these large rural lands effectively, a garrison had to be placed in towns such as Strasbourg. Indeed, the bridge over the Rhine at Strasbourg had been used repeatedly by Imperial (Holy Roman Empire) forces, and three times during the Franco-Dutch War
History of Strasbourg its flourishing economy attracted many Germans. This could explain the difference between the rural vote and the one in Strasbourg. After the war, many Germans left Strasbourg and returned to Germany; some of them were denounced by the locals or expelled by the newly appointed authorities. The Saverne Affair remains vivid in the memory of many Alsatians. In 1920, Strasbourg became the seat of the Central Commission for Navigation on the Rhine, previously located in Mannheim, one of the oldest European institutions. It moved into the former Imperial Palace. When the Maginot Line was built, the "Sous-secteur fortifié de Strasbourg"