Chinese forces under General Liu Gang move to crush rebellions in China’s northern Vietnamese provinces of Tonkin and Annam, then march south in 605, defeat the army of Cham king Sambhuvarman by luring the enemy war-elephants into an area booby-trapped with camouflaged pits; the Sui forces then massacre the defeated troops, seize Ch'u-su, and sack the Cham capital at Tra-kieu.

Following the withdrawal of the Chinese forces, Sambhuvarman resumes control and obtains forgiveness from Emperor Yang of Sui.

Emperor Yang creates his wife Crown Princess Xiao empress, and Yang Zhao crown prince, in spring 605.

He also abolishes the offices of military commandants.

He, at this time, trusts Empress Xiao's brother Xiao Cong the Duke of Ju (Western Liang's last emperor) and makes him, as well as many of her other relatives, important officials, creating for him the greater title of Duke of Liang.

Starting in 605, Emperor Yang also begins a massive number of construction projects—including the building of the imperial palace at Luoyang, described to be particularly luxurious.

Further, he conscripts a large number of men to build the Tongji Canal, connecting Luoyang with the Yellow River and connecting the Yellow River with the Huai River, as well as to rebuild the Han Canal, connecting the Huai River and the Yangtze River.

The two canals, which will eventually become parts of the Grand Canal of China, are said to be constructed within five months, but at substantial cost of life—forty to fifty percent of the men employed.

Emperor Yang also orders that some forty secondary palaces be built around the empire, so that he can visit the various provinces, arguing that he needs to do so to see the conditions of the empire so that he can govern effectively.

Emperor Yang, after the Tongji and Han Canals are completed in fall 605, carries out the first of eleven (counting military campaigns) tours that he will eventually undertake of various parts of the empire, going to Jiangdu—the capital of Yang Province, where he had been commandant previously—on an imperial ship that is said to be sufficiently large and luxurious to serve as a floating palace.

Also in 605, when Khitan tribes attack Ying Province (roughly modern Zhaotun, Liaoning), Emperor Yang has the official Wei Yunqi requisition Tujue troops under Ashina Rangan to attack the Khitan.

The Khitan forces are caught by surprise and defeated.

Construction had begun on the Anji Bridge ("Safe crossing bridge") in Hebei Province during the Sui Dynasty (China).

The world's oldest open-spandrel stone segmental arch bridge, credited to the design of a craftsman named Li Chun, the bridge has been constructed in the years 595-605.

Located in the southern part of Hebei Province, it is the oldest standing bridge in China.

Khosrow crosses the Euphrates to take Hierapolis and Beroea (Aleppo).

Internal dissensions have made the eastern Roman provinces easy prey, and the Persians overrun Armenia and central Asia Minor, though they apparently do not permanently occupy or administer them.

Yang Zhao the Crown Prince becomes ill while visiting Luoyang in summer 606, and soon dies.

Emperor Yang will not create another crown prince for the rest of his reign, creating Yang Zhao's sons Yang Tan, Yang Tong, and Yang You imperial princes, while initially apparently tacitly considering his second son, Yang Jian the Prince of Qi, the de facto successor, leaving Yang Jian in charge of Luoyang whenever he is away from Luoyang.

Yang Su, whom Emperor Yang pretends to respect but actually fears, dies in summer 606.

Also in 606, Emperor Yang orders that two massive food storage facilities—the Luokou Storage and the Huiluo Storage—be constructed near Luoyang.

Harsha Vardhana, a sixteen-year-old prince of the former Gupta vassal kingdom of Thaneswar (Sthanvisvara), near Delhi, is enthroned in 606 following the slaying of his elder brother by Shashanka, the king of Gauda.

Harsha, who inherited the throne by agreeing to share power with his sister, the widowed queen of the Maukharis, moves his capital from Thaneswar to the Maukhari capital of Kananuj.

Aiming to avenge his brother’s death and restore the scope of the Gupta empire, Harsha, allies with King Bhaskaravarman of Kamarupa.

Gaining influence from Assam in the east to Gujarat in the west, Harsha will over the next several years rebuild his kingdom on a feudal rather than a centralized basis.

Ashina Rangan visits Emperor Yang at Luoyang in spring 607.

At the instigation of Yuwen Shu Emperor Yang has Yang Yong's eight sons put to death around the same time.

Emperor Yang abolishes provinces in summer 607 and changes them to prefectures.

At the same time, he reorganizes his father's governmental system of having five main bureaus, keeping four of the main bureaus—the executive bureau (Shangshu Sheng), the examination bureau (Menxia Sheng), the legislative bureau (Neishi Sheng), the archival bureau (Mishu Sheng)—while abolishing the eunuch bureau and replacing it with the palace bureau (Diannei Sheng).

He establishes three additional independent agencies and five independent departments.

He also organized the imperial army into sixteen corps.

He abolishes three levels of noble titles—the counts, the viscounts, and the barons—keeping only the princes, the dukes, and the marquesses.

Also in summer 607, Emperor Yang embarks on a tour of the northern provinces, building an imperial highway from Chang'an to …