Qu Hui wrote:One of the reasons that Liu Biao did not attack Cao Cao was a lack of available troops. In 207, Liu Biao probably had near the 100,000 troops he had in 200. Cao Cao's army had probably five times that number, if not more. If Biao had attacked, he would have lost.
Uh...where are these numbers coming from? They seem way too high.
Cao Cao at his HEIGHT would have had maybe 300,000. And that's including garrisons he needs to defend his many many many many fronts.
I highly disagree with the assessment that it was a military issue. Cao Cao was known to be cautious but there's only so many ways you can stretch so many men. He probably would have had a few thousand near the border, no more than one hundred thousand below the yellow river with no capable commanders except Xun Yu. And communication would have been near impossible. Cao Cao's cream troops, esp. the Qing Zhou troops and elite cavalry were all in the north. I don't think a successful attack could have completely destroyed Cao Cao militarily but it would may have put Liu Biao on equal footing with Cao Cao. As opposed to awaiting inevitable surrender/defeat like he ended up doing. Would have forced the court to move from Xu Chang to Ye most likely.
But that's just the military issues. In reality I do agree Liu Biao, even if he had been capable and decisive, had numerous really good reasons not to attack Cao Cao, some of them mentioned here. Firstly he wasn't a warlike man. As said, Jing Zhou at the time prospered because it was a peaceful region in a world embroiled in war. Talents and refugees from everywhere flocked to Liu Biao (such as Liu Bei). I don't think Liu Biao wanted to invite war on that. Besides if he went to war there's a chance he couldn't surrender to the court when the time came and live in peace/moderate power in all likelihood.
And secondly as mentioned by Jiang Cheng, Liu Biao did not trust Liu Bei. Liu Bei was renowned the world over at the time, as a talent and an ambitious man who could not serve under others. (This always baffled me, since he did no great deeds really and just suffered defeat after defeat at that time. I guess he must have been, as everybody suspects, a really extraordinary man).