While King Geunchogo fought fiercely with the northern kingdom of Goguryeo, he sought to improve relations with other neighboring states. Baekje allied with the southeastern Korean kingdom of Silla in 366 and established diplomatic relations with Japan in 367. The king is known as the first Baekje king whose name was recorded in a Chinese history book. According to The Book of Jin, Geunchogo sent an envoy to the Jin Dynasty of China in the year 372. This is believed to have been the first diplomatic contact between the two kingdoms. In the same year, Jin also sent a mission to Baekje. During the king’s reign, Baekje took the lead in the so-called triangle trade with China and Japan, emerging as a new trading center of East Asia.

One of the most remarkable achievements of the king was brisk exchanges with the Wa kingdom of Japan during the Yamato period. The king invited Japanese envoys to the Baekje court and demonstrated his kingdom’s strength and wealth by showing a number of rarities such as silk, bows made of bulls’ horns and iron products. The friendly relations between Baekje and Japan are well evidenced in a special weapon called the Seven-Branched Sword, which Geunchogo gave to the Yamato leader. Geunchogo also sent two scholars named Wang In and Ajiki to Japan to spread Confucian classics, Chinese characters and Baekje culture. The Japanese ruler is said to have had the Baekje scholars teach the crown prince.

At home, King Geunchogo ordered scholar Koheung to compile a history of Baekje with the purpose of highlighting the dignity of the royal court and solidifying the state system. Unfortunately, the history book is no longer in existence today.

The king built a very strong nation, which the neighboring states were all afraid of. Thanks to the trading routes explored by the king, Baekje people were able to expand their presence in Japan, China and even Southeast Asia. Some scholars say Baekje was able to create such a liberal and splendid culture thanks to this king’s achievements. Under his reign, the kingdom reached its greatest height in territory expansion, economy and culture. It would be fair to say that he was the most celebrated monarch of the Baekje Dynasty, under whose rule Baekje was the strongest in its history. He died in 375, ending his 29-year rule.