The four evils refer to reverse osmosis, psychological warfare, policy and stealing secrets, which are the contents of the unremitting struggle of the hidden front. The work of covert struggle is to ensure safety, overall situation, victory and combat effectiveness. This paper profoundly expounds the position, function and great significance of doing a good job in covert struggle in future wars.

In the future war, infiltration and reverse osmosis, psychological warfare and anti-psychological warfare, rebellion and counter-rebellion, stealing secrets and anti-stealing secrets will certainly run through the whole process of military struggle. Therefore, we must further improve our ideological understanding, intensify the work of "four evils", do a good job in active and offensive warfare, and prevent the enemy from "going in and going out."