After entering in over half a dozens sectors worth of planets, I've gotten the impression that standing armies (...and navies) in the Traveller universe are as prohibitively expensive in that world as in ours. Only the major powers (...and thus, major races) can really afford to have serious standing armies. Many of the planets in the feudal confederation of the Third Imperium simply don't have the resources, organization or wherewithal to put together more than a token system defense force.
Shalom,
Maksim-Smelchak.
Armies (and wet navies) are expensive, but space ships are too affordable. Even only allocating 10% of the military budget to Space defence of Torpol and Clarke they have 5 or 6 antique SDB's and 200+ TL8 through 11 Fighters
(just using the ships from Traders & Gunboats), which is more than enough to stop the Pirate attack in the first adventure.
The main problem is all the class A and B starports.
Kind regards
David