A Simple Concept When Put Simply
This is an idea used in military strategy, including any video game hailing from Asia. That this is technically Japanese is almost besides the point; the idea goes back to ancient China, to the point that I saw what I would consider a mistranslation of this (well, a less than ideal translation) yesterday when reading about the Battle of Guandu between Cao Cao and Yuan Shao in the Three Kingdoms period of China.
So, let’s get this out of the way.
The two sections here are “hon” (which, strictly speaking, would be read as real, but which we might view as main – bear with me), and “tai” which simply means body. But, this is not sufficient on its own. As we are discussing a military “body,” let us refer to it as the main force.
This is as opposed to detachments such as: scouting forces (偵察部隊 (teisatsu butai), lit. “reconnaissance units”), vanguard units (先遣部隊 (senken butai), lit. “advance dispatch units), and so forth.
Thus, if one barely defeats the vanguard unit, and the 本体 (= main force) arrives, you’re in a heap of trouble.
The alternate translation I saw was “main army,” which is not really a good way to put it. That’s because people will use “hontai” to refer to the main force regardless of the size, and the term could easily be applied to an army group, with a single army (or even two or three) breaking off from the main force to attack a flank.
Of course, this would work with smaller forces as well. A platoon could break off from the main force of the size of a company.
This is such a basic and integral part of Asian military thinking that it really needs to be understood. In Asian thinking, the primary host is a single force, from which components are created, split off, and re-absorbed.