Unifying the North is a great contribution of Cao Cao to history. One side has been a valiant soldier all his life, and his attempt to unify the whole country here is not so obvious. It can be said that Cao Cao privately didn't want to see the Han Dynasty fall apart, and he didn't even want the situation that the three countries were divided. Everything is not voluntary by Cao Cao. All he can do is to try his best to keep the foundation of the Han Dynasty under the given situation, so as not to be carved up by Yuan Shao and Sun Jian.
The system of wasteland reclamation refers to the army's agricultural production to supply military needs, but after the war, the army had to recuperate, so civilians could only be allowed to cultivate land for production. Of course, this is rewarding, so people are willing to do such a thing, so that the army's arsenal will be full. Recruiting talents is also something that must be done during the war years, and it must be done unremittingly.
Because talent is the guarantee and foundation to win the war, what Cao Cao has done really shows that he can't wait to collect all the talents and dig corners bit by bit, even if it is disloyal. As long as it is a talent, there is a share of Cao Cao. This can be seen from Sima Yi. Even though he knew that Sima Yi was unavailable, he was appointed, which also shows that Cao Cao has a strong self-confidence to ensure that his people can be used by himself.