In my humble opinion, the Tang dynasty was prosperous largely in comparison with what came before.
From the end of the Han through the Wei and Jin dynasties, the Northern and Southern dynasties, and on into the Sui and Tang, regimes rose and fell, and the people were driven from their homes.
The northern tribes grew powerful, the frontiers remained unsettled, palace factions fought bitterly, and internal strife never ceased. Then Gaozu raised an army in Jinyang and brought together the achievements of all under heaven. Taizong governed with tireless dedication, bringing peace to the realm. Only then came the prosperity of Zhenguan and Kaiyuan.
The people were good and simple. They sought enough food and clothing to get through each day, longed for a peaceful home and a livelihood, wished to see their children and grandchildren gathered around them, and hoped to die a natural death. That was what they called prosperity.
Yet when things reach their extreme, they must turn in the opposite direction. Prosperity gives way to decline, and after the An Lushan Rebellion, the glory of the High Tang steadily faded.
The book Tang in Turmoil recounts events from Taizong's Xuanwu Gate Incident, through Wu Zetian's seizure of the throne and the An Lushan Rebellion, to Huang Chao's uprising at the end of the Tang, offering an exploration of what the High Tang's prosperity truly meant.
In my humble opinion, the Xuanwu Gate Incident disrupted the royal order but did not imperil the state. With the speed and force of a thunderbolt, Li Shimin put an end to the threat posed by his brothers and shouldered Gaozu's worries. Though later generations condemned him, his actions benefited the age in which he lived.
The turmoil caused by Wu Zetian lay within the imperial clan. She seized the Tang throne to replace it with Zhou, and the Li and Wu clans took up arms against each other. Corrupt officials added to the suffering, while favored servants abetted the chaos.
In the end, however, she returned power to the Li family and restored order. The merits and faults of the great empress will be judged by posterity.
The An Lushan Rebellion arose from the system of regional military governors, but its cost was paid by the common people. All under heaven suffered unbearably: in the morning, they bathed among the lotus blossoms at Huaqing Palace; by nightfall, they lay in the dirt beneath Mawei Slope.
Afterward came the turmoil of imperial relatives and the disasters wrought by palace eunuchs. By the end of the Tang, the roots of the chaos lay in the hearts of the people.
