I'm doing a little more world building, and I'm looking at how my two rival factions would go about preparing to go to war one day. In the world I have constructed, there is a 30 year cold war that has only avoided becoming hot because neither side thinks they can win.
On one side is Krasnovia. They are Russian revolutionaries who took over the moon with the backing of German industry. Operating from the moon, they have a population nearing 1 billion. Most resources are present for the taking on the Moon, or can be easily imported from Earth.
On the other is the International Space Treaty Organization. They are a bunch of asteroid belt colonies in a mutual defense pact. Some are high tech. Some are huge. Some are little fiefdoms that just happen to produce something of value. Others are just little fiefdoms. Population wise, they have 1/3 of the people of Krasnovia. However, in the last war they were able to fight Krasnovia to a standstill.
Krasnovia's issues are that the bulk of their armed forces are dedicated to planetary control. If you need something the size of the moon conquered, they can do it. They just need to land their Army first. Their Navy is designed to keep other people's Armies from landing. They are optimized for high intensity conflict, preferably a Mahanian massive final battle. However, transport and logistics are not their strong suit.
Also, given the sheer number of other competing goals in Krasnovia, keeping that fleet in top readiness at all times is also not their strong suit. Most of the fleet is currently in mothballs.
ISTO's issues are that they are trying to repel a larger Navy that is better equipped (at least on paper) with a fraction of the budget. Oh yes, and that budget needs to be shared with the civilian transportation industry.
The ISTO approach was to ban civilian ownership of spacecraft, and make sure that every ship that is constructed can serve some kind of war time purpose. This basically means that there are no "cheap" ships. Everything is built to naval specifications, even if it is just hauling water back and forth. Or... at least some relaxed sense of Naval specifications. They may not necessarily have armor and weapons installed at the factory. But the vessel's frame and propulsion are sizes with those add-ons in mind, and there are all of the attachment points and conduits pre-run to allow a vessel to be converted in very short order.
Commercial interests lease these overbuilt ships. And over time a set of arcane commercial rules forbid travelling from one port to another in ISTO on a non ISTO-flagged vessel. In practice, this fleet is heavily subsidized and is consistently out-competed by foreign flagged vessels from the Circle Trigon whose vessels can be built to sub-commercial specifications. And to get around the rules about port-to-port travel, the Circle Trigon has established a series of neutral ports that vessels can sail from and to for minimum fuel to bypass the tariffs.
These "Neutral Ports" have practically no civilization to speak of, collect nothing in the way of resources, and in fact exist solely the facilitate trade on the cheap.
The question is, when war comes, who would "win".
Krasnovia has more ships, and more population to man those ships. But by this point in history, their population is going to have to re-learn how to fly them. They are also going to need to restore these vessels to fighting condition after decades in mothballs.
ISTO's entire fleet has been under continual maintenance and operation for the cold war. But, now trying to mobilize that fleet means cannibalizing their transportation network.
Who would win depends on how long the war drags out. If ISTO managed to get in a first strike, they could pretty much control all of the lines of communication around the Solar System for the first 6 months. But like the Japanese in WWII, every vessel and crew lost would be very hard to replace.
With that said, a loss of space transport doesn't really effect Krasnovia that much. All of their worlds are large enough to sustain themselves and a wartime industrial base. Lessons from the war of '62 have shown that nobody's space fleet does well against planetary defenses.
Conversely, as ISTO is made up of colonies that each produce a limited set of resources, and interruption in transportation could cripple their wartime industry. Psyche has steel and population, but not water or fuel. Ceres has water and fuel, but virtually no population. Other colonies each have a niche product that the refine or manufacture. But without a steady supply of raw material and finished goods, they cease to become productive.
Victory depends very much on the length of the conflict. ISTO has no real way to keep Krasnovia from dragging things out. Krasnovia knows it's going to have a demoralizing opening to the war. And up until now, there really hasn't been anything to fight that hard over.