Hashshashin
Up to the Middle Ages and perhaps a bit beyond, it was possible to wage what I would call private wars. That is, a war started by a person and funded fully by that person. But as the cost and theater of war expanded, it became increasingly difficult, if not impossible for one person to afford it.
That is not to say private wars no longer exist. Even in the present, some local conflicts, such as those funded by the drug cartels, may fall under this definition.
But what seems to be emerging is a return to private wars in the sense that, through the use of terrorist techniques first developed in Arabic countries, one person can literally fund and execute a war against, for example, a country.
The logistics of a private war is made easier by several factors. We live in a global economy with global transportation systems. A lone terrorist can be in Baghdad today and Boston tomorrow. We also have the freedom to move around the country without being challenged.
We have global money systems in which funds in Nassau can be transferred, in an instant, to an account in New York.
We live in an open society in which information, such as what is needed to create a bomb is readily available on the Internet. Even the parts to cook such a lethal recipe is readily available in country.
All of these ingredients make it possible for one well financed person to wage war on a country.
Royal Australian Air Force Group Captain Peter Layton has written an essay that looks carefully at the rise of the hashshashin, from which we get the word assassin, and how they are characteristic of "The New Arab Way of War." While I don't necessarily agree with all his essay says, there is much to learn from it.
As an aside, he footnotes the word assassin thusly:
The word assassin seems particularly applicable to the foot soldiers of the modern Arab way of war. Assassin is used here as one who kills, or attempts to kill, by surprise or secret assault; or one who treacherously murders anyone unprepared for defense. The name comes from the Assassins of the East, followers of the Shaikh al-Jabal (Old Man of the Mountain). This was a Muslim order active in Persia and Syria about 1090-1272 whose members believed their religious duty was to harass and murder their enemies. The word derives from medieval Latin assassinus, which is derived from the Arabic hashshashin, and first appeared in English early in the 1600s.
Aloha!