Size of the Legions

General
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1

So, I’m sure some of you have occasionally wondered just how big the Imperial Military Service actually is, in practice. Here are some very rough numbers based on some wild approximations you can noodle around with:

The Empire’s population as of the default year is canonically around 2.57 trillion.

To a first approximation, the peacetime military has roughly 0.25% of that population under arms. This is, in many people’s opinion, rather bloated, but somehow they’ve ended up with all sorts of commitments to various satrapies, client-states, and allies, and so it goes. This makes the total strength of the Imperial Military Service something around 6.425 billion sophonts.

About 60% of this goes to the Legions, who are by far the most manpower-hungry branch. Boots on the ground, and all that. That gives us 3.855 billion legionaries. With a tooth-to-tail ratio I approximate as around 0.3, call it a fighting strength of 1.156 billion.

Or to put it another way, the Legions can field roughly 77,000 legions at full strength at any given time.

(It is also worth noting: if you want to count drones towards the total fighting strength, multiply by six and add a bit.)

2

Your tooth-to-tail ratio is impressively high. In WW2, the US Army was running at about 0.1, with 9 or 10 people for every combat soldier.

3

Well, they do have 8000 years of equivalent advancement against our contemporary abilities to play around with.

4

Some of that is that the Imperial Service has a fully integrated administration and logistics division that the Imperial Military Service takes advantage of, so there’s a gain in piggybacking off existing facilities and not suffering from duplication of effort and lack of taking advantage of best practices.

But mostly it reflects how there’s always been a high degree of automation at the back end, necessarily so, for the same reasons that it’s true everywhere else there .