Why couldn't the Tang Dynasty compare with the Sui Dynasty in its heyday?

The Tang Dynasty was the first unified Central Plains dynasty without the Great Wall since Qin Dynasty. The Complete Tang Poetry contains more than 5, Tang poems, and there are more than 2,3 famous poets in the Tang Dynasty, which is twice as many as the poems from the Western Zhou Dynasty to the Southern and Northern Dynasties combined. During the Zhenguan period of Emperor Taizong, the East Turkic was conquered and captured, and Jie Likan, the highest leader of the East Turkic, was honored as Tiankhan by the four foreign countries. Later, Emperor Taizong sent troops to conquer and destroy Gao Changguo, which blocked and controlled the Silk Road, and the Khanate of Qiuci and Xueyantuo, which were often against the Tang Dynasty. During the Zhenguan period, in order to transport the grain and materials from Bashu area in Sichuan to Chang 'an, the capital city, the waterway of Commendation and Xiedao was built, connecting Bashu Hanzhong with Meixian County in Baoji, Shaanxi.

During the Yonghui period in Tang Gaozong, Emperor Li Zhi sent generals Cheng Yaojin, Xu Maogong, Su Dingfang, Xue Rengui and Zheng Rentai to wipe out Goguryeo, West Turkic and other countries successively. Liu Rengui, a general, was sent to defeat the Japanese allied forces in the naval battle at Baijiangkou, with a land area of 12.37 million square kilometers, reaching Lake Baikal in the north and controlling the Qingling area in the west. During the Tang Zhongzong period, the 67-year-old Empress Wu Zetian forced her son Tang Zhongzong Li Xianchan to abdicate the throne, and the northern grasslands and countries in the western regions rebelled, reducing the land area to more than 6 million square kilometers. After that, the Turks revived and controlled 4, strings. After the Dragon Coup, Wu Zetian was transferred to his son Tang Zhongzong Li Xian, and Emperor Zhongzong listened to the advice of Prime Minister Cui Zhuo, and built the Danba Waterway, connecting Danshui in Hanjiang River in Hubei Province and the capital Chang 'an Suishui, and continuously transported the grain and materials in the middle and lower reaches of the Hanjiang River to Chang 'an, the capital.

during the kaiyuan period in Li Longji, Xuanzong of the Tang dynasty had a population of more than 8 million, and the post-Turkic khanate was conquered through joint Uighur. General Gao Xianzhi, Wang Zhongsi, and Li Siye were sent to conquer other countries, and the Arab black-clad eater suffered from military expansion to the east in Central Asia. The famous Battle of da Ross took place. Because the Geluolu people suddenly defected to the Tang army, the Tang army was defeated by the Arab army in Da Ross. After this war, the Arab black-clad eater army saw the power of the Tang army and dared not expand to the east. Shortly after that, the Anshi Rebellion took place, and the troops of the Tang Dynasty were transferred eastward to quell the rebellion. Since then, Central Asia has been separated from the Central Plains for thousands of years, and it has become Islam when it goodbye.

during the Tang dynasty, more than 3 countries paid tribute to the Tang dynasty. In the Kaiyuan period of Li Longji, Emperor Xuanzong of the Tang Dynasty, the feudal society in China reached its peak in economy, politics, culture and military affairs. After the Anshi Rebellion, through the unremitting efforts of three emperors, Su Zong, Dai Zong and De Zong, the Anshi rebels were divided and disintegrated, but the remnants continued to make trouble in three towns in Hebei. Later, after Emperor Xianzong's vassal-cutting, the situation of Yuan and Zhongxing was created, and then after Tang Wuzong's Huichang Zhongxing and Tang Xuanzong's rule of Dazhong, the national power of the Tang Dynasty was revived.