Background: Thomas Nast (; German: [nast]; September 27, 1840 - December 7, 1902) was a German-born American caricaturist and editorial cartoonist considered to be the "Father of the American Cartoon". He was the scourge of Democratic Representative "Boss" Tweed and the Tammany Hall Democratic party political machine.
Context: In February 1860, he went to England for the New York Illustrated News to depict one of the major sporting events of the era, the prize fight between the American John C. Heenan and the English Thomas Sayers sponsored by George Wilkes, publisher of Wilkes' Spirit of the Times. A few months later, as artist for The Illustrated London News, he joined Garibaldi in Italy. Nast's cartoons and articles about the Garibaldi military campaign to unify Italy captured the popular imagination in the U.S. In February 1861, he arrived back in New York. In September of that year, he married Sarah Edwards, whom he had met two years earlier.  He left the New York Illustrated News to work again, briefly, for Frank Leslie's Illustrated News. In 1862, he became a staff illustrator for Harper's Weekly. In his first years with Harper's, Nast became known especially for compositions that appealed to the sentiment of the viewer. An example is "Christmas Eve" (1862), in which a wreath frames a scene of a soldier's praying wife and sleeping children at home; a second wreath frames the soldier seated by a campfire, gazing longingly at small pictures of his loved ones. One of his most celebrated cartoons was "Compromise with the South" (1864), directed against those in the North who opposed the prosecution of the American Civil War. He was known for drawing battlefields in border and southern states. These attracted great attention, and Nast was called by President Abraham Lincoln "our best recruiting sergeant".  After the war, Nast strongly opposed the Reconstruction policy of President Andrew Johnson, whom he depicted in a series of trenchant cartoons that marked "Nast's great beginning in the field of caricature".
Question: What did he do to oppose the policy?

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