The phenomenon of war provides a very clear and immediate glimpse into the tensile fields that any kind of action must take place in.
You can't simply jump from a life as a domestic householder to a state of constant warfare. Depending on the culture you are brought up in, you may be accustomed to violence and violent acts, and it may be easier to enter a state of warfare. Especially if you are threatened, the instincts kick in, the body and mind become accostomed to violent acts, and the acts come easier.
In a rich society, where warfare is non-existent inside of its walls, the professional warrior must be developed by a process of breaking them in. Their spirits must be crushed, and they must be subjected to artificial hardship. The warrior has to be forged through a kind of directed trauma and torture. You can't simply take a civilian and pitch them into total warfare, contrary to what Hollywood would have us believe anyway. However it does help the institutions of war to draw from the urban and rural poor, who may already be hardened to an extent.
But then as war becomes regularized, it reproduces itself through cycles of revenge and a will to power. And in peacetime the warrior finds the mundane civilian life tortuous, or the warrior suffers from PTSD and replays the trauma in the psyche. The warrior then must be tranquilized and slowly re-assimilated into a normal life.
It is in this way that action begets itself, and then reinforces itself at a certain critical threshold, until it passes yet another threshold in which it begins to beget its opposite, its antagonistic actions. Or otherwise it peters out and some other dominant state of action re-asserts itself.
