More than 20,000 km long, the Great Wall of China consists of walls, natural barriers and trenches. A true fortification, it played a decisive role in the seizure of power, the reign and fall of empires and dynasties. From 221 BC, the first Chinese emperor, Qin Shi Huang, at the head of the Qin dynasty, succeeded in unifying China by waging bloody wars against his neighbors and by setting up a new state organization. Like other regions, the newly formed empire protected itself against the invasion of nomads from the north with a 5,000-kilometer-long wall. This was the beginning of the Great Wall of China.