The symbol of ancient national strength was population, so the reproduction of population became the key to the continuation and final victory of the war. And women are the only tool to reproduce. More women means more fertility. The most direct way to kill all enemy men and steal women is to reduce their reproductive capacity and increase their own, which can be said to be a strategic force.

Second, resources are scarce.

In ancient times dominated by patriarchal society, women, like gold and grain, belonged to resources, property and men. Therefore, if a person is killed, his property will naturally be kept. Moreover, the slogan of ancient wars was "rob money, rob vegetables and rob women". Women are strategic materials like money and food, and those beautiful young women are national treasures. In ancient times, there were countless wars for women, so no one wanted to kill women as a strategic material.

Third, it is easy to conquer.

In ancient times, women's resistance consciousness was very weak, and women were born feminine and cowardly. They are usually caught and rarely resist. Especially after being captured and bred by enemy countries, they are even more reluctant to leave. Therefore, you don't have to worry about resistance when you leave women. But men are different. If they don't kill, they may resist at any time. The cost and risk are incalculable, so men must die and women can't kill them.

Fourth, special purpose.

In fact, this is the selfish desire of the ruler. After the victory of the general war, they will choose beautiful and rich harem from the plundered women, or become maids or handmaids for people to drive away. Moreover, in ancient times, in addition to the promotion of officials and titles, the reward for meritorious ministers and generals was to send women, and captured women prisoners of war were the best source. Moreover, the ancient army also had official prostitutes and needed a large number of people. For example, more than 1 10,000 women captured by Jin Jun in the Song Dynasty, most of them entered the Huan Yi Courtyard and actually became official prostitutes. In addition, some cruel people in ancient times, such as the Jie people, even made enough food rations for women, and they were called bipedal sheep, which was very pitiful.