Why is rape used for war? WHAT IS THE PURPOSE?  

The porpose of the war is to kill or vanquish the opponent. The bulk of the army is of men. When they fight for a long time they are away from the family and normal civilisation. The men in the army long for the company of women. When they conquer a town or city and enter the place, they like to possess the women. Some go for prostitutes others go after the public which results in raping. Rape is not the motto of the war.