This period also allowed Japan to adopt new technologies such as torpedoes, torpedo-boats and mines, which were actively promoted by the French Navy (Howe, p281). Japan acquired its first torpedoes in 1884, and established a "Torpedo Training Center" at Yokosuka in 1886. Sino-Japanese War Japan continued the modernization of its navy, especially as China was also building a powerful modern fleet with foreign, especially German, assistance, and the pressure was building between the two countries to take control of Korea. The Sino-Japanese war was officially declared on August 1, 1894, though some naval fighting had already taken place. The Japanese navy devastated Qing's northern fleet off the mouth of the Yalu River at the Battle of Yalu River on September 17, 1894, in which the Chinese fleet lost 8 out of 12 warships. Although Japan turned out victorious, the two large German-made battleships of the Chinese Navy remained almost impervious to Japanese guns, highlighting the need for bigger capital ships in the Japanese Navy (the Ting Yuan was finally sunk by torpedoes, and the Chen-Yuan was captured with little damage). The next step of the Imperial Japanese Navy's expansion would thus involve a combination of heavily armed large warships, with smaller and innovative offensive units permitting aggressive tactics. The Imperial Japanese Navy further intervened in China in 1900, by participating together with Western Powers to the suppression of the Chinese Boxer Rebellion. The Navy supplied the largest number of warships (18, out of a total of 50 warships), and delivered the largest contingent of Army and Navy troops among the intervening nations (20,840 soldiers, out of total of 54,000). Russo-Japanese War Following the First Sino-Japanese War, and the humiliation of the forced return of the Liaotung peninsula to China under Russian pressure (the "Triple Intervention"), Japan began to build up its military strength in preparation for further confrontations. Japan promulgated a ten-year naval build-up program, under the slogan "Perseverance and determination" (Jp:臥薪嘗胆, Gashinshoutan), in which it commissioned 109 warships, for a total of 200,000 tons, and increased its Navy personnel from 15,100 to 40,800. These dispositions culminated with the Russo-Japanese War (1904–1905). The Japanese battleship Mikasa was the flagship of Admiral Tōgō Heihachirō. At the Battle of Tsushima, the Mikasa led the combined Japanese fleet into what has been called "the most decisive naval battle in history". The Russian fleet was almost completely annihilated: out of 38 Russian ships, 21