over the southern half of China after overthrowing Liu Song in 479. Both Qi and Wei tried to tighten Goguryeo's relationship with them. Wei emperors treated Goguryeo delegates as equal to Chinese delegates. Under the reign of Emperor Xiaowen alone, 41 emissaries were sent, but the frequency started to drop since Jangsu continued to keep hospitality with Qi. This decrease in exchanged delegates outraged Emperor Xiaowen, and at last he gave an order to capture Goguryeo delegates before they could reach the Qi capital. However, Jangsu paid no mind, and continued to send delegates to Qi. Northern Wei could not block Goguryeo, which indicated the success of Jangsu's diplomatic strategy: maximizing the situation and manipulating the power struggles between rival Chinese states to Goguryeo's advantage. Goguryeo and the northern states maintained peace and did not have further conflicts until the Goguryeo–Sui War in 598. Relations with southern Korean states Marriage alliances Confronted with harsh attacks from Goguryeo into the southern region of the Korean peninsula, Baekje and Silla found their survival through marriage alliances, beginning in 433. The alliance between Baekje and Silla lasted more than a century and was the primary reason why Goguryeo was unable to conquer the entire peninsula. Gaya Gaya found itself in a precarious situation due to its geographical disadvantage of being sandwiched by Baekje and Silla, and ultimately could not develop into an advanced nation. Baekje campaign and Dorim In 472, Gaero, the ruler of Baekje, sent a letter to the emperor of Northern Wei, stating that he was having trouble interacting with him due to frequent Goguryeo intervention, thus calling for military action against Goguryeo. However, Baekje failed to get its emissary back and was unable to receive the military support of Northern Wei. In response, Jangsu secretly planned to attack Baekje, which despite its losses against Gwanggaeto the Great, still held a significant power base in the Korean peninsula. In order to disarm Baekje, he sent a Buddhist monk named Dorim, who went to Gaero's court with the secret objective of corrupting the country. Gaero began to favor Dorim, playing baduk with him every day, and Dorim was able to talk Gaero into spending large sums of money on construction projects, weakening the national treasury. In 475, Jangsu launched a full-scale invasion from both land and sea against the now politically unstable kingdom of Baekje. Dorim was successful in gaining information about