Originally the term Daewongun referred to any person who was not actually the king but whose son took the throne. With his ascendancy to power the Daewongun initiated a set of reforms designed to strengthen the monarchy at the expense of the Yangban class. He also pursued an isolationist policy and was determined to purge the kingdom of any foreign ideas that had infiltrated into the nation. In Korean history, the king's in-laws enjoyed great power, consequently the Daewongun acknowledged that any future daughters-in-law might threaten his authority. Therefore, he attempted to prevent any possible threat to his rule by selecting as a new queen for his son an orphaned girl from among the Yŏhŭng Min clan, which lacked powerful political connections. With Empress Myeongseong as his daughter-in-law and the royal consort, the Daewongun felt secure in his power. However, after she had become queen, Min recruited all her relatives and had them appointed to influential positions in the name of the king. The Queen also allied herself with political enemies of the Daewongun, so that by late 1873 she had mobilized enough influence to oust him from power. In October 1873, when the Confucian scholar Choe Ik-hyeon submitted a memorial to King Gojong urging him to rule in his own right, Queen Min seized the opportunity to force her father-in-law's retirement as regent. The departure of the Daewongun led to Korea's abandonment of its isolationist policy. On February 26, 1876, after confrontations between the Japanese and Koreans, the Ganghwa Treaty was signed, opening Korea to Japanese trade. In 1880, the King sent a mission to Japan that was headed by Kim Hong-jip, an enthusiastic observer of the reforms taking place there. While in Japan, the Chinese diplomat Huang Zunxian presented him with a study called ""Chaoxian Celue"" ("A Strategy for Korea"). It warned of the threat to Korea posed by the Russians and recommended that Korea maintain friendly relations with Japan, which was at the time too economically weak to be an immediate threat, to work closely with China, and seek an alliance with the United States as a counterweight to Russia. After returning to Korea, Kim presented the document to King Gojong, who was so impressed with the document that he had copies made and distributed to his officials. In 1880, following Chinese advice and breaking with tradition, King Gojong decided to establish diplomatic ties with the United States.