The China Japan war of 1894 and 1895 was a war between the Meiji Japan and the Qing Dynasty china. This was the first Sino-Japanese war and it was primarily as a contest between China and Japan over who should control Korea  . Apart from the direct political and military destruction that came from this war, it also served to illustrate how the Opium wars of the previous century had weakened the Qing Dynasty China, both physically and in prestige. This war also helped in confirming to the world that modernization had successfully taken place in Japan from the time when Meiji was restored, unlike in China where the self strengthening movement had achieved little in terms of modernization  . As a result of this war also, the regional dominance in East Asia shifted from China to Japan. At the same time the Chinese experienced a big blow in its classical traditions as well as to the Qing Dynasty of China.
In 1854, the Japanese seclusion policy of Sakoku which was there during the era of Shoguns of Edo came to a halt after the American intervention forced Japan into open trade. During the years before the 1868 Meiji restoration and the fall of Shogunate, Japan transformed itself from a feudal society to a modern industrial society. During the same period, Japan had sent students and delegations around the world in order to learn and familiarize themselves with the western sciences and arts. Japan took this strategy not only prevent itself from foreign domination but also to enable herself compete fairly with the powerful western countries  .
Cause of conflict between china and Japan
As a new regional power, Japan turned its attention towards Korea. So as to guard its own security and interests, Japan intended to either seize Korea before another power could do it or at least make sure that Korea remained totally independent such that it could develop its resources and reform its administration without any foreign interference. A Prussian advisor at that time told the Meiji army of Japan that Korea was like a sword pointed at the head of Japan. According to  , due to their concern over state security, Japan felt that anyone meddling with Korea by deploying his or her militia there would in other words be interfering with the national security of Japan This feeling therefore led to the Japans decision to end the China's century old suzerainty over Korea. Moreover, Japan realized that acquiring control over Korea would also be beneficial to its growing industries which needed raw materials like coal and iron ore that were abundant in Korea Peninsula.
In 872, Japan sent a request to Korea asking her to open up trade and friendly relations with her. However, being ill informed on the nature of political alterations that had happened in Japan, Korea turned down the request and instead returned it with insults. In the same year a Korean magistrate placed a placard at the gate of a Japanese officer residence bearing mockery words against Japan  . The words said that Japan had become the regional laughing stock due to her adaptation of the barbarous customs. China having more influence over Korea at that time was thought by Japan to have had a hand in the insults and thus Japan demanded explanation from the China but she claimed to have no responsibility over Korea's actions.
In February 1876, Japan imposed on Korea, the treaty of Ganghwa after certain confrontations involving Japanese and the Korean isolationists. This treaty forced Korea to open itself to foreign trade and to Japan. At the same time it obliged Korea to demand her independence in foreign relations from China. This treaty was not only the first treaty made by Korea with a foreign power, but also the treaty that showed clearly the Japans important policy and intention towards Korea  . Traditionally, Korea had been a tributary state and persisted being so under China's Qing Dynasty influence. The Qing Dynasty also exerted huge influence over conformist Korean officials assembled around the royal family of Josean Dynasty. Due to their dividend interest and pressure from both China and Japan, the Korean officials themselves differed on the right decision to take. The conformists wanted to keep the traditional relationship with China while reformists wanted to create a new and closer relationship with Japan and the western countries.
At that time China had already fought in two Opium wars; which were with the Sino-French war and the British Empire war. According to  , these wars had made China so weak and drained of resources. China was therefore unable to resist political intervention and territorial encroachment by Japan and the western powers. Japan saw this China's weakness as a good opportunity to replace her influence in Korea with its own influence.
In 1882 Korean experienced a dangerous drought which led to extreme food shortage that caused much discord and hardship among its people. This drought put Korea on the verge of bankruptcy as it was unable to pay most of its debts and also could not pay remunerations to her soldiers. The Korean soldiers had so much resentment as they had not been paid for months. On July that year, a military rebellion broke out in Seoul and assisted by the population they sacked all the rice granaries there. After that the crowd attacked the palace and the barracks and then turned to the Japanese legation staff but the Japanese managed to escape by the help of a British survey ship to Chemulpo and then to Nagasaki  . As a way of response, Japan sent four warships and a battalion of troops to Korea, Seoul, to protect its interest and demand compensation. Consequently the Chinese also deployed 4,500 troops to counter the Japanese military forces.
However the conflict did not go far as in 1882, the treaty of Chemulpo was signed and the tension between the two sides subsided. The treaty stated that the conspirators will be punished and that Japan will be compensated for all its losses. The Japanese government was also to receive some money as a way of apologizing, and also receive permission to construct a station for its troops and barracks at their diplomatic legation 
In 1884 a group of pro-Japanese reformers, overthrew the Korean government whose officials were mostly the pro-Chinese conformists, through a bloody coup de-tat. However after some time, the government, by the help of Chinese troops was able to regain control over Korea by overthrowing the pro-Japanese reformers in an equally bloody coup. This second coup resulted in deaths of several reformers, burning of Japanese legation and death of a number of legation guards and Japanese citizens. These two incidents caused a stir between china and Japan, though the problem was amicably resolved by the 1885 Sino-Japan convection. Here the two sides agreed on a number of issues that would see peaceful coexistence between the two sides. China and Japan agreed to simultaneously pull out their troops from Korea; they agreed not to help Korea in their military training  . In case either of the countries decided to deploy its military forces in Korea it was supposed to notify the other. It was further agreed that there was no evidence that the Japanese soldiers and citizen had been killed by the Chinese troops and that those suspected of the deaths will be punished only when sufficient evidence was provided.
However, in spite these agreements, Japan was still determined to take full control over Korea and was therefore not happy with the Chinese attempts to hamper their influence over Korea. Moreover, after these agreements with china, no investigations on the matter followed and no one was punished for the deaths. On the contrary, a Chinese resident at Seoul, Yuan Shih-Kai, who was considered largely accountable for the Chinese forces behavior, was not only set free but also recalled as the Chinese minister at Seoul  . This action by the Chinese authorities caused a great displeasure among the Japanese. More displeasure however came with the clause in the convention which denied the Japanese their right to deploy their troops in Korea. China was also not happy with the terms of the convention since they required her to treat Japan on an equal basis with herself in Korea. Both countries suffered equally but after some time Japan turned down her previously acquired rights, an action that put China's suzerainty at stake. Things remained in this tight condition for nine years until 1894 when the Tonghak rebellion brought the Chinese and Japanese military forces face to face in Korea  .
In March 1894 a Korean revolutionary who was a Japanese supporter, Kim Ok-kyun was murdered in Shanghai China. Kim had sort rescue in Japan after his involvement in the 1884 coup. Later Japan turned down the Korean orders to extradite him but he was however lured to Shanghai where he was killed. His body was taken back to Korea on a Chinese warship where it was quartered and displayed as an example to the other rebels. According to the Japanese government, this was a direct affront and a drawback to her dignity and stature  . Japan held both the Koreans and the Chinese equally responsible for the affront.
Later in the year the situation worsened due to the Tonghak rebellion which broke out in Korea. The Tonghak also known as "learning of the East" was a secret party whose principles were based on a collection of tenets based upon Buddhism, Confucianism and Taoism. Its practical aims and real strength were hardly understood by the Korean government. In May 1894 the party rose in protest of the universal corruption and oppression that characterised the royal family and the entire government. The rebellions by the party were proving to be too strong for the Korean security. As a result, the Korean king requested for military force support from the Chinese, a request that the Chinese government agreed to. According to Japan this was a violation of the Li-lto convention. As a result Japan sent 8,000 troops to Korea and when the Chinese tried to reinforce their own forces, Japanese navy sank the British warship together with the Chinese reinforcement on board  . This act worsened the situation and led to declaration of war in Aug 1894.
Most of the foreign onlookers had predicted an easy victory for china over Japan but this did not happen. China had more massive forces but on the other hand Japan had earlier invested in modernization and thus had better equipments than china. Due to their modern equipments Japan achieved fast victories both on land and sea and by March 1895; Japan had successfully seized Manchuria and Shantung and also put posts that instructed sea approaches to Peking  . Unable to continue with the war, Chinese requested for peace talks with Japan but Japanese terms of negotiations were too harsh.
China's efforts to recover its control over Korea were undermined by Japan and in 1894 Japan went into war with china over Korea . In this war china's northern fleet bore the impact of the conflict with Japan as there was no assistance that the northern fleet received from the other two modern fleets of china  . Again china lost a modern marine war and had to surrender Liaotung peninsula and Formosa (Taiwan) to Japan. As a result of its defeat china had also to recognize Korean independence, to pay large compensation to Japan, to open new treaty ports, and to give unto the Japanese all the advantages that were previously taken by the western nations under the unequal treaties. The Chinese leader at that time Li, all tried to avoid this war without success. As a result his influence and reputation also suffered because of the war.
According to  , Li personally requested for peace negotiation talks with Japan in March 1895. While in Japan for this request Li was injured by a Japanese fanatic and sardonically, this attacked earned the Chinese leader so much sympathy from the Japanese that the Japanese somewhat lessened their harsh peace terms. This china Japan war which was primarily due to the desire of both countries to control Korea, marked the emergence of Japan as a key world power while on the other side it illustrated the weaknesses of Chinese empire. Though Korea had traditionally been china's most imperative client state, its strategic geographical location opposite the Japanese islands and its coal and iron natural resources, drew japans interest in it  . The real war of 1894 broke out when Japan showed plans of opening the china's closely protected kingdom of Korea, to the outside world.
Among the four reasons that led to war between china and Japan are, one the injustices that china had shown Japan since 1884. For instance deploying her army in Korea without a proper notice to the Japanese in 1884, this was a violation of the agreement between the two countries. Two; the murder of Kim Ok kuin, three, was that the Japanese felt that they had been the means of opening Korea and therefore had some right in controlling its national matters. Japan felt that by standing aside and watching China benefit solely from the work that she had already done was a great humiliation. The fourth and big reason was the political condition in Japan. The rapid transition of Japan from a despotic to constitutional rule had excited the minds of the military people against the government of the time. These military people were therefore preparing and waiting a nice opportunity to overthrow the government. When the China-Japan came by, the Japanese military which was so ready channelled all the energy to Korea which was the battle ground.
In conclusion it's also important to point out that this same problem that caused the china Japan war of 1894 is the same one that led to Japan-Russia conflict ten years latter in 1904  . Just like the other neighbouring countries, Russia's interest in Korea had grown wider and deeper during the years between 1894 and 1904. Though Russia was far more aggressive and powerful than china, Japan was still determined to protect her interests. According to the Japanese, Korea remained important to them in 1994 as it were in 1894.