On December 4, 1884, with the help of the Japanese minister Takezoe Shinichiro who promised to mobilize Japanese legation guards to provide assistance, the reformers staged their coup under the guise of a banquet hosted by Hong Yeong-sik, the director of the General Postal Administration. The banquet was to celebrate the opening of the new national post office. King Gojong was expected to attend together with several foreign diplomats and high-ranking officials, most of whom were members of the pro-Chinese Sadaedang faction. Kim Ok-gyun and his comrades approached King Gojong falsely stating that Chinese troops had created a disturbance and escorted him to the small Gyoengu Palace, where they placed him in the custody of Japanese legation guards. They then proceeded to kill and wound several senior officials of the Sadaedang faction. Consequently, within three days, even before the reform measures were made public, the coup was suppressed by the Chinese troops who attacked and defeated the Japanese forces and restored power to the pro-Chinese Sadaedang faction.
On March 28, 1894, a pro-Japanese Korean revolutionary, Kim Ok-gyun, was assassinated in Shanghai. Kim had fled to Japan after his involvement in the 1884 coup and the Japanese had turned down Korean demands that he be extradited.
On June 4, the Korean king, Gojong, requested aid from the Qing government in suppressing the Donghak Rebellion. Although the rebellion was not as serious as it initially seemed and hence Qing reinforcements were not necessary, the Qing government still sent the General Yuan Shikai as its plenipotentiary to lead 2,800 troops to Korea.
About 2,465 Chinese soldiers are transported to Korea to suppress the Donghak Rebellion.
According to the Japanese, the Qing government had violated the Convention of Tientsin by not informing the Japanese government of its decision to send troops, but the Qing claimed that Japan had approved this. The Japanese countered by sending an 8,000-troop expeditionary force (the Oshima Composite Brigade) to Korea. The first 400 troops arrived on June 9 en route to Seoul, and 3,000 landed at Incheon on June 12.
On 11/6/1894, the Donghak Rebellion has ended.
Japanese foreign minister Mutsu Munemitsu meets with Wang Fengzao, the Qing ambassador to Japan, to discuss the future status of Korea. Wang states that the Qing government intends to pull out of Korea after the rebellion has been suppressed and expects Japan to do the same. However, China retains a resident to look after Chinese primacy in Korea.
Additional Japanese troops arrive in Korea. Japanese prime minister Itō Hirobumi tells Matsukata Masayoshi that since the Qing Empire appear to be making military preparations, there is probably "no policy but to go to war". Mutsu tells Ōtori to press the Korean government on the Japanese demands.
In early June 1894, the 8,000 Japanese troops captured the Korean king Gojong, occupied the Gyeongbokgung in Seoul and, by June 25, replaced the existing Korean government with members of the pro-Japanese faction.
Ōtori presents a set of reform proposals to the Korean king Gojong. Gojong's government rejects the proposals and instead insists on troop withdrawals.
Establishment of the Japanese Combined Fleet, consisting of almost all vessels in the Imperial Japanese Navy. Mutsu cables Ōtori to take any necessary steps to compel the Korean government to carry out a reform program.
Japanese troops occupy Seoul, capture Gojong, and establish a new, pro-Japanese government, which terminates all Sino-Korean treaties and grants the Imperial Japanese Army the right to expel the Qing Empire's Beiyang Army from Korea.
On 25 July 1894, the cruisers Yoshino, Naniwa and Akitsushima of the Japanese flying squadron, which had been patrolling off Asan Bay, encountered the Chinese cruiser Tsi-yuan and gunboat Kwang-yi. These vessels had steamed out of Asan to meet the transport Kow-shing, escorted by the Chinese gunboat Tsao-kiang. After an hour-long engagement, the Tsi-yuan escaped while the Kwang-yi grounded on rocks, where its powder-magazine exploded.
On 28 July 1894, the two forces met just outside Asan in an engagement that lasted till 07:30 the next morning. The Chinese gradually lost ground to the superior Japanese numbers, and finally broke and fled towards Pyongyang. Chinese casualties amounted to 500 killed and wounded, compared to 82 Japanese casualties.
On 1 August, war was officially declared between China and Japan.
By 4 August, the remaining Chinese forces in Korea retreated to the northern city of Pyongyang, where they were met by troops sent from China. The 13,000–15,000 defenders made defensive repairs to the city, hoping to check the Japanese advance.
In early September, Li Hongzhang decided to reinforce the Chinese forces at Pyongyang by employing the Beiyang fleet to escort transports to the mouth of the Taedong River. About 4,500 additional troops stationed in the Zhili were to be redeployed. On September 12, half of the troops embarked at Dagu on five specially chartered transports and headed to Dalian where two days later on September 14, they were joined by another 2,000 soldiers.
Initially, Admiral Ding wanted to send the transports under a light escort with only a few ships, while the main force of the Beiyang Fleet would locate and operate directly against Combined Fleet in order to prevent the Japanese from intercepting the convoy. But the appearance of the Japanese cruisers Yoshino and Naniwa on a reconnaissance sortie near Weihaiwei thwarted these plans. The Chinese had mistaken them for the main Japanese fleet. Consequently, on September 12, the entire Beiyang Fleet departed Dalian heading for Weihaiwei, arriving near the Shandong Peninsula the next day.
On 15 September, the Imperial Japanese Army converged on the city of Pyongyang from several directions. The Japanese assaulted the city and eventually defeated the Chinese by an attack from the rear; the defenders surrendered. Taking advantage of heavy rainfall overnight, the remaining Chinese troops escaped Pyongyang and headed northeast toward the coastal city of Uiju. Casualties were 2,000 killed and around 4,000 wounded for the Chinese, while the Japanese casualties totaled 102 men killed, 433 wounded, and 33 missing. In the early morning of 16 September, the entire Japanese army entered Pyongyang.
The Chinese warships spent the entire day cruising the area, waiting for the Japanese. However, since there was no sighting of the Japanese fleet, Admiral Ding decided to return to Dalian, reaching the port in the morning of September 15.
Admiral Ding correctly assumed that the next Chinese line of defence would be established on the Yalu River, decided to redeploy the embarked soldiers there. On September 16, the convoy of five transport ships departed from the Dalian Bay under escort from the vessels of the Beiyang Fleet which included the two ironclad battleships, Dingyuan and Zhenyuan. Reaching the mouth of the Yalu River, the transports, disembarked the troops were and the landing operation lasted until the following morning.
On September 17, 1894, the Japanese Combined Fleet encountered the Chinese Beiyang Fleet off the mouth of the Yalu River. The naval battle, which lasted from late morning to dusk, resulted in a Japanese victory. Although the Chinese were able to land 4,500 troops near the Yalu River by sunset the Beiyang fleet was near the point of total collapse, most of the fleet had fled or had been sunk and the two largest ships Dingyuan and Zhenyuan were nearly out of ammunition. The Imperial Japanese Navy destroyed eight of the ten Chinese warships, assuring Japan's command of the Yellow Sea. The principal factors in the Japanese victory was the superiority in speed and firepower. The victory shattered the morale of the Chinese naval forces. The Battle of the Yalu River was the largest naval engagement of the war and was a major propaganda victory for Japan.
With the defeat at Pyongyang, the Chinese abandoned northern Korea and took up defensive positions in fortifications along their side of the Yalu River near Jiuliancheng. After receiving reinforcements by 10 October, the Japanese quickly pushed north toward Manchuria.
On the night of 24 October 1894, the Japanese successfully crossed the Yalu River, undetected, by erecting a pontoon bridge.
The Japanese 2nd Army Corps under Ōyama Iwao landed on the south coast of Liaodong Peninsula on 24 October.
The following afternoon of 25 October at 17:00, they assaulted the outpost of Hushan, east of Jiuliancheng. At 20:30 the defenders deserted their positions and by the next day they were in full retreat from Jiuliancheng.With the capture of Jiuliancheng, General Yamagata's 1st Army Corps occupied the nearby city of Dandong, while to the north, elements of the retreating Beiyang Army set fire to the city of Fengcheng. The Japanese had established a firm foothold on Chinese territory with the loss of only four killed and 140 wounded.
The Japanese quickly moved to capture Jinzhou and Dalian Bay on 6–7 November. The Japanese laid siege to the strategic port of Lüshunkou (Port Arthur).
Describing their motives as having encountered a display of the mutilated remains of Japanese soldiers as they invaded the town, Japanese forces proceeded with the unrestrained killing of civilians during the Port Arthur Massacre with unconfirmed estimates in the thousands. An event which at the time was widely viewed with scepticism as the world at large was still in disbelief that the Japanese were capable of such deeds that seemed more likely to have been exaggerated propagandist fabrications of a Chinese government to discredit Japanese hegemony. In reality, the Chinese government itself was unsure of how to react and initially denied the occurrence of the loss of Port Arthur to the Japanese altogether.
By 21 November 1894, the Japanese had taken the city of Lüshunkou (Port Arthur) with minimal resistance and suffering minimal casualties.
By 10 December 1894, Kaipeng (present-day Gaizhou) fell to the Japanese 1st Army Corps.
The Chinese fleet subsequently retreated behind the Weihaiwei fortifications. However, they were then surprised by Japanese ground forces, who outflanked the harbour's defenses in coordination with the navy. The Battle of Weihaiwei was a 23-day siege with the major land and naval components taking place between 20 January and 12 February 1895. Historian Jonathan Spence notes that "the Chinese admiral retired his fleet behind a protective curtain of contact mines and took no further part in the fighting." The Japanese commander marched his forces over the Shandong peninsula and reached the landward side of Weihaiwei, were the siege was eventually successful for the Japanese.
After Weihaiwei's fall on 12 February 1895, and an easing of harsh winter conditions, Japanese troops pressed further into southern Manchuria and northern China. By March 1895 the Japanese had fortified posts that commanded the sea approaches to Beijing. Although this would be the last major battle fought; numerous skirmishes would follow. The Battle of Yinkou was fought outside the port town of Yingkou, Manchuria, on 5 March 1895.
the Japanese had begun preparations for the capture of Taiwan. However, the first operation would be directed not against the island itself, but against the Pescadores Islands, which due to their strategic position off the west coast would become a stepping stone for further operations against the island. On March 6, a Japanese expeditionary force consisting of a reinforced infantry regiment with 2,800 troops and an artillery battery were embarked on five transports, sailed from Ujina to Sasebo, arriving there three days later.
On March 15, the five transports were escorted by seven cruisers and five torpedo boats of the 4th Flotilla, left Sasebo heading south to the Pescadores .
The Japanese fleet arrived at the Pescadores during the night of March 20, but encountered stormy weather. Due to the poor weather, the landings were postponed until March 23, when the weather cleared.
On the morning March 23, the Japanese warships began the bombardment of the Chinese positions around the port of Lizhangjiao. A fort guarding the harbor was quickly silenced. At about midday, the Japanese troops began their landing. Unexpectedly, when the landing operation was underway, the guns of the fort once again opened fire, which caused some confusion among the Japanese troops. But they were soon silenced again after being shelled by the Japanese cruisers. By 2:00pm, Lizhangjiao was under Japanese control.
After reinforcing the captured positions, the following morning, Japanese troops marched on the main town of Magong. The Chinese offered token resistance and after a short skirmish they abandoned their positions, retreating to nearby Xiyu Island. At 11:30am, the Japanese entered Magong.
The Japanese warships entered the strait the next day and, upon discovering that there were no mine fields, they entered Magong harbor.
The Treaty of Shimonoseki was signed on 17 April 1895. The Qing Empire recognized the total independence of Korea and ceded the Liaodong Peninsula, Taiwan and Penghu Islands to Japan "in perpetuity".
Several Qing officials in Taiwan resolved to resist the cession of Taiwan to Japan under the Treaty of Shimonoseki, and on 23 May declared the island to be an independent Republic of Formosa.
On 29 May, Japanese forces under Admiral Motonori Kabayama landed in northern Taiwan, and in a five-month campaign defeated the Republican forces and occupied the island's main towns.
The campaign effectively ended on 21 October 1895, with the flight of Liu Yongfu, the second Republican president, and the surrender of the Republican capital Tainan.