How did Taizong’s style of rule change in the latter half of his reign?

In the latter half of his reign, the Taizong emperor’s style of rule shifted significantly from the collaborative approach that characterized his earlier years. While he was initially renowned for governing as a "first among equals" who actively sought and accepted outspoken criticism from his ministers, he became increasingly arbitrary and impatient with such feedback as his reign progressed.1

This period was also marked by a decline in his firm grasp over court politics, exacerbated by a bitter struggle regarding the succession after his original heir apparent was banished. During these later years, Taizong became more assertive and made few new administrative innovations, focusing instead on perfecting existing institutions and reorganizing the military. His earlier, highly idealized style of government—which relied on a close, ethical interplay between the sovereign and his advisers—diminished as he grew less receptive to the very counsel that had previously defined his "era of good government".123