A TL 7 drop ship of sorts

[Enoki]

So all bets are off if the system is not roughly similar to Earth with most of the govermnents being democracies. Corporate governments do whatever the corporation wants, and dictatorships of all stripes are at the whim of their leader.

The https://www.statista.com/statistics/1342260/wwii-mobilization-by-country/ data shows the Soviet Union mobilized 34 million (of a population of 186 million) or 1/6 the total population. I would consider that to be a high limit sort of figure as the Soviets were pretty thorough in drafting everyone available, though if women are eligible to be drafted , that doubles your pool, too. Also, the pool of eligibles was inflated by the WW1 post-war baby boomers just hitting 18-22, prime drafting age.

Sort of yes and no.

It comes down to what the people are doing locally. Say a corporation is running some mines on the planet to extract resources. They own the towns, they own the mines, and they import everything they see as necessary to keep the miners working without striking and such. They don't have to produce anything or grow food locally, they bring it in on the ship(s) hauling the refined ore out.

A dictator is the same exact way. The dictator wants a massive terraforming project on a marginal planet. The dictator brings in thousands, tens of thousands, of political prisoners, assorted scum, and other "undesirables" from the home world to do the work along with guards and such. Everything is imported to ensure control of the population. You want food? Meet your work quota...

As for a military, let's say the planet is over-populated for the amount of resources locally available. Cannon fodder is a great way to kill two problems with one artillery shell so-to-speak. The reverse can be true too. Too many people? Pack a bunch in a ship and send them on a one-way flight to some marginal planet to "colonize" it. Half die? Oh well... You can send more. The ship is designed that when it arrives it's only real value is as scrap resources to help build the colony. That way nobody can escape...

 

[Condottiere]

Also, if everyone owns an assault rifle, because of local environmental conditions.

 

[Commander Truestar]

The reverse can be true too. Too many people? Pack a bunch in a ship and send them on a one-way flight to some marginal planet to "colonize" it. Half die? Oh well... You can send more. The ship is designed that when it arrives it's only real value is as scrap resources to help build the colony. That way nobody can escape...

This exists in the OTU.
If you go through the TAS reports in the JoTAS, you will find a storyline where the overpopulated Bevey (Some stories and documents spell it Bevy) system forcibly colonized the Kegina system with waves of their excess population until destabilization of the Kegina government caused Duke Leonard to step in with forces available to him.

So, @Enoki is dead on