Koryo is one of critical kingdoms in Korean history during 10th and 14th century. During Koryo era, cultural aspect of the country flourished in many ways. For example, blue ceramic is a clear demonstration of creativity. Moreover, Koryo made a lot of cultural exchanges with foreign countries, such as contacting with Thailand and Islam cultures. These contacts made the country to experience international differences and contributed to the outgrowth of the country. Unfortunately, Koryo went through extreme chaos at the end of the era. Koryo started to decline because of the invasions of foreign countries, new rules on land policy and the advent of ambitious general, Yi Songgye.
             Despite of many mutual exchanges with foreign countries, Koryo was attacked and invaded by China and Japan constantly. When a country is attacked by another country numerously, the country loses control on inner affairs and becomes unstable and easier to decline. Geographically, Northern part of Korea is connected to China. Therefore, it was easier for China to invade Korea. At the end of Koryo era, which was 1359, Koryo was attacked by a group called Red Turbans (Han, 178). These aggressive Red Turbans were defeated by the Mongol army (Mongolia was the country right above Northern Korea) and about 40,000 Red Turbans fled to Koryo. They occupied four Northwest towns and took Pyongyang, but they were defeated by Koryo army (Han, 178). However, Red Turbans returned again with 100,000 strong men. All the Northern part of Koryo were destroyed and corrupted. This time, Kaesong (Capital city of Koryo) was in danger. The court had to move down to Andong, which was located in the South. By moving the court, Koryo wasted a lot of capital money. The cost of lives and resources that have been lost from these attacks were the causes of decline. Mongolians have been attacking Koryo on and off for many years before the Red Turbans. For example, in 1231, ...