During their short reign, the Sui dynasty had made a significant amount of changes. When China was finally reunited in 588 CE, it's first emperor was Yang Jian and its capital was Chang'an. During his reign, China saw a significant spread in Buddhism and witnessed the construction of the Grand Canal. The military was also powerful, successfully fighting off the threat of invaders to the west and north. Yang Jian's successor's reign, Yang Guang, saw both the height and decline of the Sui. Guang completed the project of the Grand Canal, extended the Great Wall of China and brought more territory under Sui control. However, in doing this, he spent too much labor and money on these projects that when he sent a campaign to Korea, not only was it unsuccessful but it led to many protests and a ba