The port became a major seaport in the Song Dynasty. The natural harbor is deep, and can handle the biggest ships of over 100,000 tons. To defend the island from Japanese, Prince Zhou Dexing enclosed Xiamen Town with 110 kilometers of heavily fortified wall.
The ancient wall was destroyed in 1928, but you can see remnants in some places like Xiamen University. This wall was used to keep out the Japanese, but it could not keep out the Europeans however. They came as traders initially.
Then, after the Mongols invaded and set up the Qing Dynasty, a famous person named Koxinga who was born in 1629 in Hirado, Japan set up a territory in the area outside Qing control. He fought against the Qing troops and also drove the Dutch from Taiwan. When he had control, the territory’s name was called Siming that means "Remember the Ming".
It is now the name of a district in Xiamen. The Dutch had colonized Taiwan. So on April 21, 1661, he set sail with tens thousands of troops (perhaps 25,000), and the Dutch surrendered on January 27, 1662. He is famous in both Chinese mainland and Taiwan for these victories. Koxinga died soon after this, and then the Qing Dynasty took over the Xiamen area.
In 1902, the area had a local government composed of foreigners. There were foreigners of many countries in the International Settlement, and fourteen countries had consulates there. In 1939, the Japanese wanted to invade the area, but couldn’t due to the presence of foreign troops. In 1941, the Japanese controlled the area.
In 1980, it became one of China’s first four special economic zones where foreign investment and international trade was allowed. After this, the city became prosperous. The city relies heavily on foreign trade and investment for growth. It is a vital port for trade with Taiwan and is an important passage for Taiwanese to visit Chinese mainland.