South Korea's history began with Dangunwanggeom's Gojoseon. Gojoseon was conquered by Han China. After Gojoseon collapsed, there were a lot of countries such as Buyeo, Okjeo, Dongyae and Samhan. But Baekje, Goguryeo and Silla were the strongest. So their period began, and it is called the Three Kingdoms Period. Goguryeo and Baekje were conquered by Silla and Dang China's allied forces, and Silla unified the three kingdoms. There was another country, Balhae. Balhae was founded by Dae Jo-Young. Later Silla and Balhae's period is called South and North Countries Period. A rebellion in Later Silla caused the birth of a new nation: Goryeo, which was founded by Wanggeon. Mongolia's invaded Goryeo. Near the end of the Goryeo period, there was a great general Lee Seong-Gye. The king of Goryeo directed him to occupy Yodong, but he opposed. However, Lee Seong-Gye went to Yodong to occupy it, but he returned to Goryeo and he revolted. His revolt succeeded, and he founded the country Joseon. Joseon's first king, Taejo, moved the capital to Hanyang (Seoul). Joseon's fourth king, Sejong, made the Korean alphabet, "Hangeul". Joseon's twenty-second king, Jeongjo, built Hwaseong Fortress in Suwon. Joseon's twenty-sixth king, Gojong, changed the country's name to Daehanjeguk. When Daehanjaeguk's power weakened, Japan occupied it for 35 years until Japan's defeat in World War II in 1945. In 1950, there was a big war, the Korean War. As a result, Korea was split into two countries, North and South.