Michael Laitman, On Quora: “What is the difference between a just war and a holy war?“
I would put it this way: A just war is an individual, a group or a country fighting to defend its existence and territory. If certain forces attack with the intent to eliminate or overthrow the individual, group or nation, then the subject in defense of itself has the justification to battle in order to save its own life, the lives of its people and its borders. About this principle it is written, “If he has come to kill you—kill him first” (Tractate Sanhedrin, 72:1, Gemarah).
Countries should not attack other countries, even in certain “humanitarian” forms. They should only use the aid of international forces when they try to achieve peace or some kind of a dialogue. However, they should not wage war and employ military force.
This is why the only just war is if outside forces attack with the intent to kill, and in response, the individual/group/nation in defense of itself has the right to rise up against the aggressor and kill them, and even to be the first to start the war. If, however, outside forces have not risen up against an individual, group or nation with the intent to kill them, then no war can be waged, no matter what the excuse.
Based on a Q&A with Kabbalist Dr. Michael Laitman on September 9, 2006. Written/edited by students of Kabbalist Dr. Michael Laitman.