Crown Prince Friedrich Wilhelm, who later became Emperor Friedrich III, began regularly using the Neues Palais again in 1862 as his summer residence. Emperor Wilhelm II even made it his primary residence from 1888 to 1918. A subterranean corridor was built in 1889 that connected the service rooms in the southern Communs with the palace. The Marstall (imperial stables; now Building 8) was completed in 1894 and served as a riding arena. Emperor Wilhelm II signed the order for German mobilization in the Neues Palais on July 31, 1914. This was the start of the First World War. It was also the beginning of the end of the residence: on November 14, 1918, the remaining members of the imperial family left the Neues Palais.