_Isabella von Agypten_ (1812). Arnim's _Samtliche Werke_ were edited by his widow and published in Berlin in 1839-1840; second edition in 22 vols., 1853-1856. Selections have been edited by J. Dohmke (1892); M. Koch, _Arnim, Klemens und Bettina Brentano, Gorres_ (1893). _Des Knaben Wunderhorn_ has been frequently republished, the best edition being that of A. Birlinger and W. Crecelius (2 vols., 1872-1876). See R. Steig, _Achim von Arnim und Klemens Brentano_ (1894). ARNIM-BOYTZENBURG, HANS GEORG VON (1581-1641), German general and diplomatist, was born in 1581 at Boytzenburg in Brandenburg. From 1613 to 1617 he served in the Swedish army under Gustavus Adolphus, took part in the Russian War, and afterwards fought against the Turks in the service of the king of Poland. In 1626, though a Protestant, he was induced by Wallenstein to join the new imperial army, in which he quickly rose to the rank of field marshal, and won the esteem of his soldiers as well as that of his commander, whose close friend and faithful ally he became. This attachment to Wallenstein, and a spirit of religious toleration, were the leading motives of a strange career of military and political inconstancy. Thus the dismissal of Wallenstein and the perilous condition of German Protestantism after the edict of Restitution combined to induce Arnim to quit the imperial service for that of the elector of Saxony. He had served under Gustavus many years before, and later he had defeated him in the field, when in command of a Polish army; the fortune of war now placed Arnim at the head of the Saxon army which fought by the side of the Swedes at Breitenfeld (1631), and indeed the alliance of these two Protestant powers in the cause of their common religion was largely his work. The reappearances of Wallenstein, however, caused him to hesitate and open negotiations, though he did not attempt to conceal his proceedings from the elector and Gustavus. During the Lutzen campaign, Arnim was operating with success at the head of an allied army in Silesia. In the following year he was under the hard necessity of opposing his old friend in the field, but little was done by either; the complicated political situation which followed the death of Gustavus at Lutzen led him into a renewal of the private negotiations of the previous year, though he did nothing actually treasonable in his relations with Wallenstein. In 1634 Wallenstein was assassinated, and Arnim began at once more active operations. He won an important victory at Liegnitz in May 1634, but from this time he became more and more estranged from the Swedes. The peace of Prague followed, in which Arnim's part, though considerable, was not all-important (1635). Soon after this event he refused an offer of high command in the French army and retired from active life. From 1637 to 1638 he was imprisoned in Stockholm, having been seized at Boytzenburg by the Swedes on suspicion of being concerned in various intrigues.