Auguste Robert in the Dogger Bank. The schooner was abandoned; Dutch fishermen rescued her crew. Franco-Prussian War At the outbreak of the Franco-Prussian War in 1870, the greatly numerically inferior Prussian Navy assumed a defensive posture against a naval blockade imposed by the French Navy. Friedrich Carl and the broadside ironclads Kronprinz and , along with the small ironclad ram Prinz Adalbert, had been steaming in the English Channel before the French declared war; they had left Plymouth on 10 July with the intention of steaming to Fayal in the Azores. On the 13th, however, they put into port and learned of the rising tension between France and Prussia. The ships therefore returned to Wilhelmshaven immediately, arriving on 16 July. France declared war on Prussia three days later on 19 July. Friedrich Carl, Kronprinz, and König Wilhelm were concentrated in the North Sea at the port of Wilhelmshaven. They were subsequently joined there by the turret ship Arminius, which had been stationed in Kiel. Despite the great French naval superiority, the French had conducted insufficient pre-war planning for an assault on the Prussian naval installations, and concluded that it would only be possible with Danish assistance, which was not forthcoming. The four ships, under the command of Vizeadmiral (Vice Admiral) Eduard von Jachmann, made an offensive sortie in early August 1870 out to the Dogger Bank, though they encountered no French warships. Friedrich Carl and the other two broadside ironclads thereafter suffered from chronic engine trouble, which left Arminius alone to conduct operations. Friedrich Carl, Kronprinz, and König Wilhelm stood off the island of Wangerooge for the majority of the conflict, while Arminius was stationed in the mouth of the Elbe river. On 11 September, the three broadside ironclads were again ready for action; they joined Arminius for another major operation into the North Sea. It too did not encounter French opposition, as the French Navy had by this time returned to France. Through the 1870s, the German armored fleet typically saw active service during the summer months. Over the winter, most of the vessels were placed in reserve with one or two kept in a state of reduced commission as guard ships. In June 1871, the screw corvette was in Brazil while on an overseas cruise; some of her crew had been arrested following a fistfight in the country. The Germans threatened to deploy Kronprinz, three more corvettes, and