In China, the Sui dynasty had risen and conquered the Chen Dynasty of the south. They invaded Vietnam (northern Vietnam had been in Chinese control since the Han dynasty), fighting the troops of Champa, who had cavalry mounted on elephants. After decades of economic turmoil and a failed invasion of Korea, the Sui collapsed and was followed by the Tang dynasty, who fought with various Turkic groups, the Tibetans of Lhasa, the Tanguts, the Khitans, and collapsed due to political fragmentation of powerful regional military governors (jiedushi). The innovative Song dynasty followed next, inventing new weapons of war that employed the use of Greek Fire and gunpowder (see section below) against enemies such as the Jurchens.
