《汉书·纪·高帝纪上》
项羽此时虽已得知汉王东进的消息，而已经兵发齐地，就想消灭了齐以后再迎击汉兵，所以汉王得以乘机兼并魏、殷等五诸侯之兵，东伐楚。
羽虽闻汉东，既击齐，欲遂破之而后击汉，汉王以故得劫五诸侯兵东伐楚。
At this time, Xiang Yu had already received the news that the King of Han was advancing eastward, but he had already sent troops to Qi. He wanted to destroy Qi first and then attack the Han army. Therefore, the King of Han took the opportunity to annex the troops of the five vassals, including Wei and Yin, and attacked Chu in the east.