One would imagine burying the troops alive would have been more efficient than executing them in some way or another, but I suspect in a way that would require their cooperation. I wonder whether or not it would be easier to simply execute an unarmed man via weapons than it would be to get them into mass graves and keep them there while they were buried alive. It would take a heck of a lot of time to execute so many men, but would it really save time over trying to bury so many alive? That also requires graves for them.
How many swords would it take for that?
Cao's resources weren't very impressive at this point.A sword can only hew so many necks before needing to be tossed.How many executioners would he employ?And also,would it be more likely that the Yuan soldiers would revolt if they openly knew they were going to a slaughterfest?
The thing about burying them alive is that it took very few resources for Cao Cao.Though we have no details all Cao would need to contribute are the guards.The POWs could dig their own graves and then be forced in by the guarding force.
Perhaps if he had brought them home to his own territory and divided them among his troops any organized loyalty to the Yuans could have been resolved. Perhaps there are other areas in his territory they could have been used without placing them in conflict with the Yuan clan? Of course sending them back was out of the question though. How many troops did he have himself? If he was outnumbered by his surrenders he may have fears being overthrown by them, but it still leaves me a little curious about his choice to bury them alive instead of taking some other means to dispose of them. Finally, he was concerned about how he was seen by others. I wonder if burying so many troops alive is a good way to be seen in a positive light, or to encourage surrender from enemy forces down the road
The notion of him taking them to his home is one in error.Remember firstly the policy of the Later Han as I mentioned.Keeping the peasants untrained means that trained troops won't be revolting with the peasants.In this turmoiled time,revolt is an even larger issue for Cao than for the Han.I'm sure no one had forgotten Zhang Jue.
Relocating them was also impossible.These people would have families,all of whom would be in the north.They would not abandon them to go to Cao's agricultural colonies or a commandery.At best,he'd have thousands of people sneaking back into the north to be with their families,at which point they'd be easily drafted by the Yuans.
I think also that considering his image for the future was on the back burner compared to not slipping the noose around his own neck at this point.
"Two there should be; no more, no less.
One to embody the power, the other to crave it."
-Creed of the New Sith-