Jian'an poetry, or Chien'an poetry (建安風骨), refers to those styles of poetry particularly associated with the end of the Han dynasty and the beginning of the Six Dynasties era of China. This poetry category is particularly important because, in the case of the Jian'an poetic developments, there is a special difficulty in matching the chronology of changes in poetry with the usual Chinese dynastic chronology based on the political leadership of the times. For example, according to Burton Watson, the first major poet of the new shi style that emerged at this time was Cao Zhi, one of the sons of Cao Cao, a family which came into power at the end of Han and developed further during the Three Kingdoms era of the Six Dynasties period.