All the UNSC forces seen in this video are replaced by the following forces and must accomplish all objectives done by the UNSC.
Navy
7th Fleet, led by Admiral Thrawn
Well, if Thrawn wins in orbit, the rest of the scenario is sort of pointless, right? Even so, the force that the Seventh Fleet composes does not appear to be particularly large, so I expect that the Covenant would have more options in regard to calling reinforcements. The Empire probably has less options considering their current domestic issues and current imperialistic expansionist policies, but given that Thrawn was assigned to this mission, it suggests the Emperor places a fair amount of interest in it.
Honestly though, not important to the actual thrust of the discussion.
Ground
Commander Cody
500 Stormtroopers (Various equipment like rockets, blasters, flame throwers, grenades, deployable shields)
Inferno Squad
100 Death Troopers
4 AT-AT's
16 AT-ST's
20 LAMBDA shuttles
20 TIE Fighters
10 TIE Bombers
No, they're probably fucked.
Twenty fighters would be short change to engage in a region about the size of Ukraine, let alone a conflict that centers around a battle that spans a planet. I can't guess as to how many fighters there were in that fan film, but my guess is that they probably brought a lot more than twenty fighters. Bombers also have limited use, since you're basically bombing your own city.
The 20 LAMBDA shuttles really don't add very much either.
As for your ground forces, they make no sense. The ISB has various battalions of around that size, but it doesn't have anything remotely close to the composition that you've given it. Looking at the sort of environment that they're going into, we're probably looking at an Armor Battalion. That gives us:
- Four Companies
- 1x Breakthrough Armor Company
- 21-37 repulsor tanks, crewed by about 131 men.
- 1x Repulsorlift Company
- 31 Repulsor Vehicles
- 8x for support
- 1x for command
- 22x combat vehicles
- Approximately 188 troops
- 2x Attack Company
- Approximately 432 men
- 16x heavy tanks
- 28x light tanks
- 18x heavy weapon repulsorlifts
- Death Trooper Company
- Probably equipped with some kind of HQ, though this may be attached to the Armored Battalion. Probably equipped with at a hundred speeder bikes.
- Inferno Squad
- I honestly don't give a fuck, they probably aren't going to make a big difference.
So a more likely military force would be around 851 troops, plus Inferno Squad. A full battalion for the US Army is a thousand troops, so that's about right. So overall, we'd have an Imperial Force of:
- 851x troops
- 69x Tanks (light and heavy)
- 18x heavy weapon repulsorlifts
- 22x combat vehicles
- 8x support vehicles
- 1x command vehicle
- 4x AT-ATs
- 16x AT-STs
- 20x LAMBDA shuttles
- 20x TIE Fighters
- 10x TIE Bombers
According to Halopedia;
Covenant carrier.
A single light Covenant carrier contains the following:
- 300x Seraph Fighters
- 200x Banshees
- 34x dropships
- 4,000x troops
From that, we can probably guess there are probably 363x Ghosts and about 45x Wraiths. Could be higher. I'm just ballparking the figures here, to be honest. Overall, the Empire does have a slight advantage in terms of ground hovercraft, but they're operating against a force over 4x larger than themselves. At least--consider that the invasion we saw may have had two or three light carriers, which would drastically increase the size of the force.
To analyze this as best we can, let's look at a couple of aspects.
Troop Quality
The Empire
Storm Troopers are of a...shall we say...LOW quality. Although the Empire does have really competent and capable Storm Troopers, they clearly pad their ranks with poorly trained idiots. We can see this in plenty of episodes in Star Wars Rebels and the various implications that their troops are weak-minded. It also makes sense from a domestic point of view. The Empire had to massively expand its military in a short time after the Clone Wars and that generally means that you aren't going for quality. Add in the corruption and so forth, we can probably expect near-Russian-level competence, though probably with more discipline, better training, and far, far less theft of government resources by the grunts, though I expect given Storm Trooper armor, someone made a killing off selling the Empire knock-off ablative armor, which is something we see similar in the Russian Army. That said, basic ammo and some training is clearly present. That said, the Death Troopers are an elite group that represent the best the Empire probably has to offer. Sort of like Russia Wagner Group or other elite military units.
The Covenant
I expect the Covenant holds a mixture of low-quality, mid-quality, and high-quality troops. Troops such as Elites are obviously the cream of the crop; well-trained, well-equipped, high moral, and well-led. Brutes are sort of a mixture; very powerful, not too bright, high moral, but probably poorly led. Then of course you have things like Jackals, who are probably your mid-quality; decent gear, good training, and all that. Then of course you have the grunts, who do have high moral; they are more than willing to act as suicide bombers--but they seem poorly trained, easily spooked, and the Elites don't seem to mind using them as cannon fodder. I honestly put them below Storm Trooper competency. I also expect that the Covenant forces probably have more combat experience on average, but I can't prove that myself.
Conclusion
Overall, combat skill, discipline, and moral probably favors the Covenant. Not only do they outnumber the enemy 4 to 1, but their higher-end troops have better gear (shields, gravity hammers, cloaks, ect), but their lower end, while basically cannon fodder, can probably hold their own against the somewhat better-trained Storm Troopers.
Air Superiority
There really isn't much to discuss here. The Empire here is given a total of 20 fighters, 10 bombers, and 20 shuttles. That's not enough to contest with several hundred fighters AND a couple of hundred banshees. Even if we were to add to the numbers, the Covenant just simply has better fighters. TIEs were basically designed with the intent of being cheap and disposable. No shields, two forward lasers, and maybe a missile launcher. No co-pilot. They're maybe a match for the banshees, which are really more like A-10s if we're being honest. I sincerely doubt they can handle the Seraph Fighters.
So air superiority probably goes to the Covenant. And that's probably a pretty big deal.
Armored Forces
I actually think this is pretty even here. There are a lot of ghosts, but ghosts themselves aren't really all that useful; two fixed plasma cannons on a speeder bike is basically what they are. That's good, but it's mainly useful for scouting, flanking, mobility, or quick assaults. That sort of stuff. That said, the Covenant's wraiths are pretty damn OP here. Heavily shielded and basically a mobile heavy mortar weapon system. Of course there are other weapon systems like Spectres and the like, which I'm sure others, such as Battlegrinder will be able to bring up. My guess is they probably have at least 80x of those. Those are much better for direct combat, if memory serves. Still, the Covenant has a habit of sometimes using wraiths like tanks (my memory on that may be wrong), so that's a concern.
The Empire on the other hand, has some decent heavy and light tanks that probably can roughly match Covenant firepower. The AT-STs are mobile and effective against infantry, but would probably lose a fight to a Specter. The AT-ATs have massive durability and firepower advantages, but I don't see them being all that useful. They're just such huge targets that the Covenant is going to target them with banshees and wraiths. I just really don't see them lasting long without considerable resources dedicated to pinning down enemy forces or offering to guard them. And the Empire really doesn't have that sort of option here, due to numbers (and that's after I gave them more troops, tanks, and vehicles).
Conclusion
The Covenant would probably win. The Stormtroopers are outnumbered and are facing an enemy with far superior morale, in addition to a high-low mix of gear and troop quality that is considerably more potent than what the Empire fields. The best weapons that the Empire has (the AT-ATs) are giant targets that will probably be lost early in the battle. The Stormtrooper's only saving grace here is that they're probably the defenders, so they Covenant will suffer higher casualties as the attackers. Unfortunately, the technology, training, and doctrine favors the Covenant. The Covenant seems to prefer moving in small units and show fairly effective combined arms combat, where as your average Storm Trooper...well, not so much.
I think the initial assault will be where the Covenant takes the most losses; the Empire will be at full strength, with great cohesion, and good morale. Once the AT-ATs are gone, the TIEs are shot down, the Covenant establishes air superiority, and the wraiths begin to 'shell' targets relayed to them by orbit/banshees/scouts, I expect the Storm Trooper supply chains to break and fold under Covenant attacks, until the entire Imperial Battalion falls apart.