General Principle 1. Wars Cost Money. It takes a considerable amount of money to establish even a small fighting force. Soldiers must be paid, armed, trained, and moved around. This means, at a minimum, that there is a payroll for personnel, purchase of weapons, the cost of training exercises, and the considerations of supplies and logistics. This expense is greater than any poor man can readily imagine, and more than a single citizen of normal and average means can afford. Wars are therefore rarely organized by either the poor classes or men of merely ordinary means. This leads us directly to:
Corollary to General Principle 1. Rich men can best afford to initiate war.
General Principle 2. Wars make people rich. (A.) The officers who are "commissioned" (hired) to make the war are usually paid somewhat better than they would have been otherwise. Furthermore, they expect to "administer" (own) choice properties and positions in the event of victory. (B.) The foot soldiers usually are not well paid (since they are often conscripted), so they are promised the usual privilege of stealing, plundering, and despoiling the property of those that they kill, rape, enslave, or otherwise subdue. (C.) The rich men who plan the war are loath to see their inferiors do better than they, so they will carefully plan to come out of the war relatively much more prosperous than their fighting men. This leads us directly to:
Corollary to General Principle 2. Rich men stand to profit the most from the wars they initiate.
Ordinary Exception to Principles 1 and 2. It will be truly observed that small tribal conflicts do not accord with these general principles. Very small tribes living in stone-age villages, for example, do not prosecute their wars on exactly these principles. And occasionally, one can find instances of nomadic tribesmen or pirate bands who also operate in this exceptional manner. These exceptions are granted.
Further Exceptions to Principles 1 and 2. There have been some situations in recorded history where people of poor or modest means have repelled invaders. (True: but they did not initiate the war.) And there have been cases where people of poor or modest means have initiated wars and rebellions and have overthrown their overlords. We may think of colonial uprisings, etc., here. (We should note, however, that this is the result of some previous war or imposition that was previously initiated against them.)
Glorious Exception to Principles 1 and 2. The wars that are "ordained by God." Yes; though we might remark three things: First -- that the Lord God is given a lot of credit (or blame) here that I am not sure He either wants or deserves. Second, and pointedly -- Which God, exactly? Third -- not to be impious, but if we are really talking about the Lord God here, He admits that He is rich, so . . .
These ordinary and glorious exceptions do admittedly exist; but like other exceptions they prove, rather than contradict, the General Rule, which in this case combines Principles 1 and 2:
Rich men initiate wars and rich men profit from them.
This brings us to a practical starting point for inquiry into both history and current political affairs:
General Observation on the Causes of War. If you want to understand the causes of general wars, just follow the money. This may lead one to cynicism (??), enlightenment (!), conspiracy theory (!!), or shocked (!) disbelief.
Oh: and add that to your "Principles of Sun Tzu," or Clausewitz, or whomever. Hey, they could even teach this at West Point or Annapolis, if they cared to. General Smedley Butler wrote about it in 1933, after all. (But what did he know -- him just being a highly decorated Marine, and all.)