In 1206 a warlord achieved dominance over all Mongols with the title Genghis Khan and began his campaign of territorial expansion. The Mongols' highly flexible and mobile cavalry enabled them to conquer their enemies with efficiency and swiftness. In the brutal pillaging that followed Mongol invasions during the thirteenth and fourteenth centuries, the invaders decimated the populations of China, Russia, the Middle East, and Islamic Central Asia. Later Mongol leaders, such as Timur, destroyed many cities, slaughtered thousands of people and did irreparable damage to the ancient irrigation systems of Mesopotamia. These invasions transformed a settled society to a nomadic one. In China, for example, a combination of war, famine, and pestilence during the Mongol conquests halved the population, a decline of around 55 million people. The Mongols also displaced large numbers of people and created power vacuums. The Khmer Empire went into decline and was replaced by the Thais, who were pushed southward by the Mongols. The Vietnamese, who succeeded in defeating the Mongols, also turned their attention to the south and by 1471, they began subjugating the Chams. When Vietnam's Later Lê Dynasty went into decline in the late 1700s, a bloody civil war erupted between the Trịnh family in the North and the Nguyễn family in the South. More Cham provinces were seized by the Nguyễn warlords. Finally, Nguyễn Ánh emerged victorious and declared himself Emperor of Vietnam (changing the name from Annam) with the title Gia Long and established the Nguyễn Dynasty. The last remaining principality of Champa, Panduranga (modern-day Phan Rang, Vietnam), survived until 1832, when Emperor Minh Mạng (Nguyễn Phúc Đảm) conquered it after the centuries long Cham–Vietnamese wars. Vietnam's policy of assimilation involved the force-feeding of pork to Muslims and beef to Hindus, which fueled resentment. An uprising followed, the first and only war between Vietnam and the jihadists. It was crushed.