The Japanese invasion of Taiwan occurred in 1895 when the Empire of Japan crushed a republican movement on Taiwan while moving in to claim the islands ceded to them by Qing China at the end of the First Sino-Japanese War.
In 1894, the Imperial Japanese Navy destroyed the Chinese Beiyang Fleet at the Battle of the Yalu River, while the Imperial Japanese Army routed the Chinese armies in Manchuria and captured Port Arthur (Lushunkou) and Weihaiwei. As peace negotiations took place in 1895, Japan demanded the cession of Taiwan, leading China to offer to cede Taiwan and the Penghu Islands to Britain on the understanding that they would later be returned. However, Britain refused to embroil itself with Japan. On 24 March 1895, Japanese forces captured the Penghu Islands from their 5,000-strong garrison, although a cholera outbreak killed more than 1,500 Japanese occupiers shortly after. On 17 April 1895, China agreed to cede Taiwan to Japan as part of the Treaty of Shimonoseki.
However, Taiwanese notables led by Qiu Fengjia decided to resist the transfer of their island to Japan, proclaiming the Republic of Formosa on 23 May 1895 with former Qing governor-general Tang Jingsong as the island's president. However, there was little popular support in Taiwan for the proclamation of the republic, and Europe rejected the island's claims to independence despite their radical democratic manifesto. Beijing also failed to support the island.
On 22 May 1895, 7,000 Imperial Guards Division troops under Prince Kitashirakawa Yoshihisa left Port Arthur for Taiwan. However, the inexperienced guards lacked summer clothing, and their landings on Taiwan were delayed after they found Gongliao to be strongly defended. On 2 June, the Japanese invaders defeated the Chinese at Ruifang and pushed inland, taking the port of Keelung after a naval bombardment. On 3 June, China formally transferred sovereignty over Taiwan to the Japanese. After Taipei's fall, the republican leaders fled to the mainland on 4-6 June. The unpaid republican garrison of Taipei responded by deserting and looting the city, and a number of local businessmen such as Koo Hsien-jung invaded the Japanese into the city. From 7 to 9 June, the Japanese suppressed the riots, and the Chinese garrison surrendered without resistance. The Japanese proceeded to occupy Tamsui, once again battling Chinese deserters and taking several hundred Chinese soldiers prisoner. On 14 June, the Japanese established a new administration on the island and repatriated the thousands of Chinese soldiers captured at Keelung, Taipei, and Tamsui, landing them at Amoy in Fujian. On 26 June, Liu Yongfu assumed the presidency of the Republic of Formosa, whose popular support grew as the Japanese moved south. The Japanese secured central Taiwan from June to August, and they began their advance on Tainan in October. Local recruits took the lead in resisting the Japanese invasion, resulting in the Japanese summarily executing suspected guerrillas and burning down whole villages. The Chineser regulars and Hakka militias were defeated whnever they attempted to make a stand, and the 27 August Battle of Baguashan, the largest battle in Taiwanese history, doomed the Formosan resistance to defeat. On 21 October, Tainan fell to the Japanese. The Japanese lost 164 officers and men killed and 515 wounded, but casualties from disease were far fighter. Prince Kitashirakawa Yoshihisa died of malaria just days after the end of the campaign, although Formosans rumored that he had been mortally wounded at Baguashan.
For nearly two years afterwards, Formosans continued to resist the 100,000-strong Japanese garrison, who carried out the worst excesses of the war to suppress the Chinese rebels. On 26 November 1895, the last Formosan militia units were defeated at the Battle of Changhsing, By 1902, most of the Formosan guerrilla units had either been wiped out or surrendered.