Records of the Three Kingdoms: Yuan Shao moved his camp forward again and again to face Guandu, building earthen hills and tunnels; Cao Cao's troops…
Yuan Shao moved his camp forward again and again to face Guandu, building earthen hills and tunnels; Cao Cao's troops were at a disadvantage in open battle and had fewer than ten thousand men.
公亦分營與相當，合戰不利。
Location: 魏書 武帝紀 (卷01) 建安5년
Cao Cao fought without winning and returned to his camp to hold firm. When Yuan Shao shot arrows from high watchtowers and earthen mounds, Cao Cao smashed the towers with thunderbolt catapults and countered the tunneling with trenches, but his grain ran out and the people deserted.
彧報曰：「紹悉眾聚官渡，欲與公決勝敗。
Location: 資治通鑑 卷063 (원문 단락 #5186, 200년)
Place: 官渡
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