Both want to be top dog, and the ruling masters are willing to send in and sacrifice their minions. This situation needs no explanation, as human wars are equivalent in most respects. Warfare in human history has been as brutal as the restraints on the warlords will allow. They want at their command virtual killing machines who have no remorse or hesitation, but what human warlords most often get are procrastinating generals and deserting troops, even when the mission can be cloaked in humanitarian terms.
Soldiers hesitate to kill, and generals hope for compromise or a bloodless capitulation.
But what if there were no reluctance or hesitation, as where there is no remorse one does not hesitate. It is called thus as this is the result, the survivors ultimately finding their level in relationship to the other group, with one standing above the other. In these wars the soldiers are not motivated out of loyalty or a commitment to ideals, they are all like gladiators - kill or be killed. A soldier who refuses to be the perfect killing machine for his master is made an example, and a quick and painless death is out of the question. Human wars see the use of biological weapons such as nerve gas, nuclear bombs, maiming devices such as mines, psychological weapons such as reminders of home and comfort, and various wearing techniques such as starvation.