Why is the numbering system for military units so whacky?
For instance, if there's a 101st Airborne Division, shouldn't that mean that there were exactly 100 other airborne divisions before it was activated? ~
I don't know anything about the way military units are numbered, but I do know that numbering systems do not rely on quantity for their meaning. For example, if I live in Apartment 206 that does not mean there are at least 205 other apartments. I could give other examples, but you're a smart guy, you get the idea.
"Units as big as divisions are numbered in a arbitrary way. As are the corps, this keeps the enemy from knowing how many divisions you have. So as a whole the Army may at one time have three Army groups each with three corps each with four divisions but there designations won’t reflect that."
This seems to be the most logical (and short) response, but there are many others here: