The Eulsa Treaty or Japan-Korea Protectorate Treaty ((Japanese: 第二次日韓協約 Dai-niji Nitcho Kyōyaku; Korean: 을사조약 Eulsa joyak), also referred to as the "Second Japan-Korea Agreement" was signed between the Empires of Japan and Korea on 17 November, 1905. The name "Eulsa Treaty" treaty is derived from the Korean word "eulsa', which refers to the 42nd year of the sexagenary cycle.
Following the end of the Russo-Japanese War and the signing of the Treaty of Portsmouth, in which Japan’s supremacy on the Korean peninsula was acknowledged by Russia, the Japanese statesman, Itō Hirobumi, presented Emperor Gojong with a draft of the Protectorate Treaty on 15 November, 1905. He declared the contents to be final and non-revisable and insisted that the Emperor and his ministers accept its terms.
Faced with the disadvantage of having the Imperial palace occupied by Japanese Imperial Army troops, who were also deployed at strategic locations throughout the country, the Koreans were left with little alternative but to sign.
The treaty was signed on 17 November, 1905, by the Korean minister of foreign affairs, Bak Je-sun, and the Japanese minister, Hayasi Konsuke. The Emperor Gojong and the Prime Minister, Han Gyu-seol refused to sign the treaty. This treaty transferred full authority over Korea’s diplomatic relations, as well as control over all trade through Korean ports, to Japan. This would be managed by a Japan-appointed Resident-General - the first being Ito Hirobumi, who was appointed in March, 1906. By signing the treaty, Korea was deprived of its diplomatic sovereignty and became a protectorate of Japan. 
This treaty was later stated as being "already null and void" in Article II of the Treaty on Basic Relations between Japan and the Republic of Korea, which was signed on 22 June, 1965. However,many have argued that as the Koreans signed the treaty if not under duress, then certainly under the threat of military action, the treaty was illegal in terms of international law. In addition, as it was not signed by the Korean Emperor, nor the Prime Minister, it could not have been binding on the country. However, the major powers of the time did nothing to help Korea and turned a deaf ear to her pleas. 
Full text of the Agreement
|“|| Korean-Japanese Agreement
17 November, 1905
The Government of Japan and Korea, desiring to strengthen the principle of solidarity which unites the two Empires, have with that object in view agreed upon and concluded the following stipulations to serve until the moment arrives when it is recognized that Korea has attained national strength.
In faith whereof, the Undersigned duly authorized by their Government have signed this Agreement and affixed their seals:
HAYASHI KONSUKE (Seal)
BAK JE-SUN (Seal)
- Protectorate Treaty of 1904
- Japan-Korea Annexation Treaty of 1907
- Japan Korea Annexation Treaty
- Treaty on Basic Relations between Japan and the Republic of Korea
- Russo-Japanese War and Japanese Extortion of Korea’s Sovereignty
- Sakamoto Shigeki; "The Issue of Treaties between Japan and Korea - from the standpoint of international law"; page 373
- Sakamoto Shigeki; "Effect of the Korea-Japan Treaty - the first anthology"; Kansai University Law No. 44 Volume 4; 1995.