soldiers provided the bulk of the infantry. For the purpose of cavalry, the Wei was similar to the previous Han dynasty in recruiting large numbers of Xiongnu that were settled in southern Shanxi. In addition, provincial armies, which were very weak under the Han, became the bulk of the army under the Wei, for whom the central army was held mainly as a reserve. This military system was also adopted by the Jin dynasty, who succeeded the Wei and unified China. Advances such as the stirrup helped make cavalry forces more effective. Era of division In 304 AD, a major event shook China. The Jin dynasty, who had unified China 24 years earlier, was tottering in collapse due to a major civil war. Seizing this opportunity, Xiong-nu chieftain Liu Yuan and his forces revolted against their Han Chinese overlords. He was followed by many other barbarian leaders, and these rebels were called the "Wu Hu" or literally "Five barbarian tribes". By 316 AD, the Jin had lost all territory north of the Huai river. From this point on, much of North China was ruled by Sinicized barbarian tribes such as the Xianbei, while southern China remained under Han Chinese rule, a period known as the Era of Division. During this era, the military forces of both Northern and southern regimes diverged and developed very differently. Northern Northern China was devastated by the Wu Hu uprisings. After the initial uprising, the various tribes fought among themselves in a chaotic era known as the Sixteen Kingdoms. Although brief unifications of the North, such as Later Zhao and Former Qin, occurred, these were relatively short-lived. During this era, the Northern armies, were mainly based around nomadic cavalry, but also employed Chinese as foot soldiers and siege personnel. This military system was rather improvising and ineffective, and the states established by the Wu Hu were mostly destroyed by the Jin dynasty or the Xianbei. A new military system did not come until the invasions of the Xianbei in the 5th century, by which time most of the Wu Hu had been destroyed and much of North China had been reconquered by the Chinese dynasties in the South. Nevertheless, the Xianbei won many successes against the Chinese, conquering all of North China by 468 AD The Xianbei state of Northern Wei created the earliest forms of the equal field (均田) land system and the Fubing