Looking over the events of the battle of Chi Bi, one thing kept bothering me about Cao Cao's strategy. The Chang Jiang is a very long river. Why in the world, with such a preponderance of numbers, did he concentrate all his troops in one place? It seems to me that if he had divided his army, keeping all of his detatchments larger than Wu's main body, and placing them at different points on the river, he would badly overextend Wu's already weak defenses, lengthen the odds that all of their troops could be defeated by strategems from Kongming or Zhou Yu, and also have an opprotunity of outflanking Wu's forces altogether and forcing them into a land battle.
Did the terrain make this impossible, was it just considered bad military strategy at the time, or was there another reason Cao felt compelled to concentrate his forces at Chi Bi? Does anyone know?