to cannon fire. One of the first screw-driven warships, , demonstrated her superiority over paddle steamers during numerous trials, including one in 1845 where she pulled a paddle-driven sister ship backwards in a tug of war. However, paddle warships were used extensively by the Russian Navy during the Crimean War of 1853–1856, and by the United States Navy during the Mexican War of 1846–1848 and the American Civil War of 1861–1865. With the arrival of ironclad battleships from the late 1850s, the last remaining paddle frigates were decommissioned and sold into merchant-navy service by the 1870s. These included , which became one of the first Boston steamers in 1867. Paddle minesweepers At the start of the First World War, the Royal Navy requisitioned more than fifty pleasure paddle steamers for use as auxiliary minesweepers. The large spaces on their decks intended for promenading passengers proved to be ideal for handling the minesweeping booms and cables, and the paddles allowed them to operate in coastal shallows and estuaries. These were so successful that a new class of paddle ships, the Racecourse-class minesweepers, were ordered and 32 of them were built before the end of the war. In the Second World War, some thirty pleasure paddle steamers were again requisitioned; an added advantage was that their wooden hulls did not activate the new magnetic mines. The paddle ships formed six minesweeping flotillas, based at ports around the British coast. Other paddle steamers were converted to anti-aircraft ships. More than twenty paddle steamers were used as emergency troop transports during the Dunkirk Evacuation in 1940, where they were able to get close inshore to embark directly from the beach. One example was , which saved an estimated 7,000 men over the nine days of the evacuation, and claimed to have shot down three German aircraft. Another paddle minesweeper, , was deliberately beached twice to allow soldiers to cross to other vessels using her as a jetty. The paddle steamers between them were estimated to have rescued 26,000 Allied troops during the operation, for the loss of six of them. Modern paddle steamers China In order to thank the Qing government for its support of Japan in the Russo-Japanese War, Japan specially built a yacht called "Yonghe Steamer" for Cixi, which, from the outside, should be a steam-propelled structure, with waterwheel-like waterwheels on both sides to push the ship forward. It can be viewed