While Mongols were fighting among themselves, in 1368, Zhu Yuanzhang extended his rule to Guangzhou. By 1387, all of China was liberated by Zhu Yuanzhang. As the new emperor, Zhu Yuanzhang was given the title Hong Wu and founded the new dynasty, the Ming. The first concern of China's new emperor in 1370 was military strength and preventing Mongol resurgence. Hong-Wu established garrisons at strategic points and created a hereditary military caste of soldiers who would sustain themselves by farming and be ever ready for war. Hong-Wu made his commanders new military nobility. Troops were forbidden to abuse civilians. He banned secret societies. Hong-Wu worked toward economic recovery. Farms had been devastated, and he settled a huge number of peasants on what had been wasteland and gave them tax exemptions. Between 1371 and 1379 the land under cultivation tripled, as did revenues. The government sponsored tree planting and reforestation. Neglected dikes and canals were repaired and thousands of reservoirs were rebuilt or restored. Hong-Wu died in 1398, at the age of 70. The man who had managed to rise to power and found a dynasty was followed by sons less able than he. Hong-Wu's death was followed by four years of civil war and the disappearance of his son and heir, Jianwen. Jianwen had been indecisive and scholarly and no match for his uncle, who in 1403 became the emperor. Zhi Di, also known as the Emperor of Yongle, said to have been born of a Korean concubine. Emperor Yongle ruled to 1424 and used eunuchs as spies and appointing them to high positions in government. One of Emperor Yongle's eunuchs, Zheng He, was a Muslim whose father had made a pilgrimage to Mecca. He knew the world a little more than others, and he led a group of can-do eunuchs that