In 1959, Peng Dehuai wrote a letter to Mao, in which he compared himself to Zhang Fei: because of Mao's popular association with Cao, Peng's comparison implied that he had an intuitively confrontational relationship with Mao.
Peng Dehuai wrote a letter to Mao. This was in 1959. He compared himself to Zhang Fei in Mao. He had an intuitively confrontational relationship with Mao. Peng's comparison implied this. This was because of Mao's popular association with Cao.