This was originally part of a discussion of “big fleet” actions in a small ship setting on the Traveller discord, and how to let these actions in the background affect players while not making it feel like the background is just sitting pre-created and waiting to nab them. I mentioned that I make heavy use of GM and NPC emulators for this sort of thing, and someone wanted to see a detailed example.

I love worldbuilding, and this is all based on a custom setting I developed. 24 inhabited systems, linked by about the same number of uninhabited systems, spread out over a few subsectors. Two major polities, a small but centralized one, and a larger confederation. So it’s very much a small ship, small universe setting. It’s also a pretty hostile universe, with only a couple of worlds that are even remotely terraformable, so those are extremely valuable. In this setting, no jump drives capable of better than Jump-2 exist.

Historically, there have been conflicts between the two polities before, and stretches of cold war. The larger polity (the Alliance – I know, lame name) has recently been weakened because of a civil war, and the smaller polity (the UTSC) is taking advantage of this, and has invaded. The UTSC admiral who came up with the plan, Admiral Antonini, was put in charge of the invasion force. I used an NPC generator to give me a one-liner for him:

A proud warrior, motivated to achieve victory, safeguard force, and achieve myths.

The impression I got from this is that he’s an older admiral who’s thinking about his legacy, wanting to return lost UTSC territory to their control (with himself as military governor of the conquered territory, of course). He’s also cautious, prone to probing attacks instead of risky battles.

This is important, because it lets me imagine the possibilities that he would consider. I don’t make any firm decisions for him, however. Those are controlled by a GM emulator – a set of tables that answer yes/no questions.

Hai Zhe is the nearest UTSC stronghold. Fomalhaut is a neutral party. Dupree used to be an Alliance system, but the starport station in the system was partially destroyed, and the system held by the UTSC as they drove into Medusa and Aiea. Rasalhague is the jewel of this particular area, home to the only planet in the subsector where food can be easily grown. The UTSC naval forces are stronger than the Alliance forces in this area of strength, but Rasalhague is still heavily defended. The UTSC concentrates its force in Medusa, with a smaller force in Dupree (to maintain the route to Hai Zhe), and a defending force in Hai Zhe which the UTSC will not commit to the invasion.

Alliance Admiral Nieves (A sinful outlaw. Motivated to achieve myths, secure riddles, and associate the church.), in charge of a smaller but significant force rimward (“south”) of this map has been gathering intelligence, and thinks Antonini is overextended. He has been trying to convince Alliance Admiral Hu (A pious courtier. Motivated to conceive the elite, manage enlightenment, and administer the elite.) to link up to invade Dupree, but Hu feels this would expose them to an attack by UTSC reserves rimward. Nieves figures he has to act alone, then, and that if he succeeds Hu will support him.

Nieves has sent a small force to Fomalhaut demanding that they stop allowing the UTSC to stage through their system, or he will consider them to be allies of the UTSC, and treat them as hostile. Fomalhaut is not a wealthy or powerful system, and so they agree. Nieves figures that this might delay the UTSC from resupplying the invasion force, and so he takes this opportunity to make a risky attack on Dupree, capturing the system and cutting off Antonini.

Antonini is currently in Medusa, which is an untenable spot for him. The two options for him would be to either strike Dupree and retake it (which would cost him a portion of his force, limiting his ability to continue the invasion), or strike Rasalhague in the hopes that victory here would push the UTSC into retaking Dupree. Since Antonini is thinking about his legacy, I ask the GM emulator about invading Rasalhague first:

Q: “Will Antoniti attack Rasalhague?”
A: Yes, but…

So he will, but there’s some hesitancy. I probe into this:

Q: “Will he attack this month?”
A: No

Q: “Will he attack next month?”
A: Yes

So clearly he’s gathering his forces, gathering intelligence. The PCs (detached duty scouts) are in Rasalhague at the time. The atmosphere at Rasalhague Station is tense, with people expecting an invasion force at any time. I had already checked if the scout base there wanted to reactivate the PCs, and got the answer “no, but…”, so I figure I will recheck that if conditions change. The PCs are contacted by someone who wants to leave the system, and so they gather some cargo and head out to Serurier. They do their business in Serurier, and end up taking a lucrative contract to bring supplies into Rasalhague. Timing-wise, they will arrive at Rasalhague a few days after Antonini launches his attack, so I need to work that out.

There’s a set of mathematical formula that’s useful in military strategy called Lanchester’s Laws. They basically determine who would win in a fight between unequal numbers of forces. In my setting, the very largest ships are 6000 dton, with no book 5 weapons or anything. Limited to 1 turret per 100 tons, military ships boost their force by carrying fighters and SDBs. Missiles are the primary offensive weapon, with lasers being secondary offensive weapons and anti-missile defenses, and both sides of a battle field similar sorts of forces – lots of fighters, carriers focusing on defense, etc. The battles themselves are mostly contests of fighters, with the winner of that contest engaging the opposing carriers.

This is similar to infantry battles between forces armed with guns (battles at a range greater than contact, with choice of target, and heavy offense versus defensive abilities). Lanchester’s Square Law deals with this and says the side with the greater numbers wins, and that their effectiveness is proportional to the square of their numbers. For instance, if side A brings 300 fighters to a battle, and side B has 400, the ratio is 3/4. But the square of the ratio is 9/16, so side B would win and retain 43.75% of their forces: 175 fighters. This forms the basis for how I determine who wins a big naval battle in my game.

Back to the invasion of Rasalhague! Antonini jumps in with 4 carriers and an assault ship, carrying 427 fighters. The Alliance forces consist of one small carrier, and 284 fighters. I divide the battle into days. Each day I make a roll to see what percentage of the forces engage, and I roll to see how effectively they deploy. Effectiveness is a small fudge factor onto the strength ratio, just to add some uncertainty. I make rolls day-by-day and determine that the battle takes 3 days. At the end of this time, Antonini has lost one carrier and about 230 fighters, while the Alliance carrier fled and the system otherwise fell.

This tells me that when the PCs jump in, the system has been newly conquered. Antonini has been working to organize food shipments to Medusa and Aiea. Time for the GM emulator:

Q: “Is Rasalhague cooperating with the food shipments?”
A: Yes, but…

Q: “Are there problems with merchants being attacked by the UTSC forces?”
A: Yes

Q: “Does this mean that merchant families are getting out of Rasalhague?”
A: Yes

Q: “Does this threaten Antonini’s ability to supply Medusa and Aiea?”
A: Yes

So the PCs jump in to a powderkeg situation. Antonini desperately needs to regain cooperation of the merchant families – in my setting, large merchant ships are owned by families – but he’s also concerned about possible Alliance smugglers. So Rasalhague Station contacts the PCs, informing them that they are now in UTSC territory, and they need to dock at Rasalhague Station to get UTSC trade papers. There is a lot of UTSC naval traffic, so the implication to the PCs is that there is an unspoken “or else…”

The PCs don’t have the fuel to immediately jump out, and refueling at a gas giant would take too long, so they decide to dock at Rasalhague Station. Once there, they are informed that there is a delay processing papers… There are a lot of merchants docked there, and they’re all angry at the delays…