How did the early Tang poetry develop?

Poetry in the early Tang Dynasty did not change rapidly with the unification and prosperity of politics and economy. On the contrary, the poetic style of Qi and Liang continued to dominate the poetic world with the power of emperors. Yu Shinan in the period of Emperor Taizong and Shangguan Yi in the period of Emperor Gaozong are both representatives of the favorite court poems of the emperor. Shen Quanqi and Song also created a large number of court poems in the post-Wu period, but they inherited the achievements of their predecessors and completed the creation of five-character and seven-character poems, which made certain contributions to the development of poetry. The key to the change of poetry style in Tang Dynasty lies in the struggle between the new poetry school representing the interests of middle and lower landlords and the court poetry school. During the period of Emperor Gaozong, four outstanding poets in the early Tang Dynasty rose. Although they haven't completely shaken off the influence of the poetic style of Qi and Liang Dynasties, they have put forward the idea of "lightness" and "backbone" and are deeply dissatisfied with the poetic style of the court represented by Shangguan Yi. Their poems either express their ambition to join the army and serve the country, or expose the dissolute emptiness of aristocratic life, or express their grief and indignation. The theme has expanded and their thoughts and feelings have begun to change.