As for Cao Cao's decision to send troops against Nanyang, it had not been a coincidence.
In the original course of events, Cao Cao had fought Nanyang for several years, from the second year of the Jian'an Era all the way to the Battle of Guandu.
Almost whenever he had a spare moment, Old Cao had to dispatch troops to Nanyang.
On one hand, the Battle of Wan City had forged a blood-deep enmity between the two sides.
On the other hand, Nanyang was the gateway to Xu County!
Geographically speaking, Nanyang was separated from Guanzhong and Luoyang by mountain ranges to the north.
To the south lay Liu Biao's territory; to the east it led straight to Yingchuan; to the west, one could reach Hanzhong.
This geography dictated that if Liu Biao wanted to advance north, he had to open a breach through Nanyang!
And if Cao Cao wished to properly defend the Central Plains, he had to use Nanyang as a strategic buffer behind him.
Thus, Nanyang was virtually territory that Cao Cao and Liu Biao were bound to fight over.
According to the original course of events, after Old Cao's defeat at Wan City, he would have returned to campaign against Yuan Shu before continuing his attack on Zhang Xiu.
But with Qin Tian's reversal of the realm's situation, Cao Cao had not had another chance to launch a major campaign against Nanyang since last winter.
Then, in April and May of this year, Cao Cao had clashed with Liu Bei in the Central Plains.
This made Cao Cao increasingly worried about the current state of the realm, and he wanted to find a way to break the deadlock!
In the original course of events, Old Cao had already begun plotting against Xuzhou at this time.
But