Emperor Taizong of Tang (Chinese: 唐太宗; pinyin: Táng Tàizōng, Wade-Giles: T'ai-Tsung, January 23, 599 – July 10, 649), personal name Lǐ Shìmín (Chinese: 李世民), was the second emperor of the Tang Dynasty of China, ruling from 626 to 649. As he encouraged his father, Li Yuan (later Emperor Gaozu) to rise against Sui Dynasty rule at Taiyuan in 617 and subsequently defeated several of his most important rivals, he was ceremonially regarded as a cofounder of the dynasty along with Emperor Gaozu. He is typically considered one of the greatest, if not the greatest, emperor in all of Chinese history. Throughout the rest of Chinese history, Emperor Taizong's reign was regarded as the exemplary model against which all other emperors were measured, and his "Reign of Zhen Guan" (Simplified Chinese 贞观之治/ Traditional Chinese 貞觀之治) was considered a golden age of Chinese history and required study for future crown princes. During his reign, Tang China flourished economically and militarily. For more than a century after his death, Tang China enjoyed peace and prosperity. During Taizong's reign, Tang was the largest and the strongest nation in the world. It covered the entire territory of present day China and much of central asia. It laid foundation for the Xuanzong reign, which is considered China's greatest period of time.