He was descended from the old family of von der Tann, which had representatives in Bavaria, Alsace and the Rhine countries, and assumed his mother's name (she being the daughter of an Alsatian, Freiherr von Rathsamhausen) in 1868 by licence of the king of Bavaria. Ludwig, the first king of Bavaria, stood sponsor for the child, who received his name and in addition that of Arthur, in honour of the Duke of Wellington. He received a careful education, and in 1827 became a page at the Bavarian court, where a great future was predicted for him. Entering the artillery in 1833, he was after some years placed on the general staff. He attended the manoeuvres of the Austrian army in Italy under Radetzky and, in the spirit of adventure, joined a French military expedition operating in Algiers against the Tunisian frontier.
On his return he became a close personal friend of the Crown Prince Maximilian Joseph (afterwards King Maximilian). In 1848 he was made a major, and in that year he distinguished himself greatly as the leader of a Schleswig-Holstein light corps in the Danish war. At the close of the first campaign he was given the order of the Red Eagle by the king of Prussia, and his own sovereign gave him the military order of Max-Joseph without his asking for it, and also made him a lieutenant-colonel. In 1849 he served as chief of staff to the Bavarian contingent at the front, and distinguished himself at the lines of Düppel, after which he visited Haynau's headquarters in the Hungarian war, and returned to Schleswig-Holstein to serve as v. Willisen's chief of staff in the Idstedt campaign.
Then came the threat of war between Prussia and Austria, and von der Tann was recalled to Bavaria. But the affair ended with the "surrender of Olmütz," and he saw no further active service until 1866, rising in the usual way of promotion to colonel (1851), major-general (1855), and lieutenant-general (1861). In the earlier years of this period he was the aide-de-camp and constant companion of the king. In the war of 1866 he was chief of the staff to Prince Charles of Bavaria, who commanded the South German contingents. The almost entirely unfortunate issue of the military operations led to his being vehemently attacked in the press, but the unreadiness and unequal efficiency of the troops and the general lack of interest in the war on the part of the soldiers foredoomed the South Germans to failure in any case.
He continued to enjoy the favour of the king and received promotion to the. rank of general of infantry (1869), but the bitterness of his disappointment of 1866 never left him. He was grey-haired at-forty-two, and his health was impaired. In 1869 von der Tann-Rathsamhausen, as he was now called, was appointed commander of the I. Bavarian corps. This corps he commanded in the Franco-German War, and therein he retrieved his place as one of the foremost of German soldiers. His gallantry was conspicuous at Worth and Sedan. Transferred in the autumn to an independent command on the Loire, he conducted the operations against d'Aurelle de Paladines, at first with marked success, and forced the surrender of Orleans. He had, however, at Coulmiers to give way before a numerically larger French force; but reinforced, he fought several successful engagements under the Grand Duke of Mecklenburg near Orleans. On the termination of the war he was reappointed commander-in-chief of the I. Bavarian corps, a post which he held until his death at Meran. He had the grand cross of the Bavarian military orders, and the first class of the Iron Cross and the pour le merite from the king of Prussia. In 1878 the emperor named von der Tann chief of a Prussian infantry regiment, decreed him a grant, and named one of the new Strassburg forts after him.
See Life by Lieutenant-colonel Hugo von Helvig in Mil. Wodien-blatt, Supplement, 1882.
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