Page "Sui Dynasty" Paragraph 13

Both Emperors Wen and Yang sent military expeditions into Vietnam as Annam in northern Vietnam had been incorporated into the Chinese empire over 600 years earlier during the Han Dynasty ( 202 BC-220 CE ).

However the ancient Kingdom of Champa in southern Vietnam became a major counterpart to Chinese invasions to its north.

According to Ebrey, Walthall, and Palais, these invasions became known as the Linyi-Champa Campaign ( 602-605 CE ).