Forerunners vs. Galactic Empire

[ThePerson5]

So, this battle pits the Forerunners at the height of their power against the Galactic Empire, also at the height of it's power. We now know more about the Forerunner's capabilities since Halo: Cryptum has been released, so here are some quotes from the novel:

Pages 11 and 51

Twenty kilometers away, the central peak of Djamonkin
Crater rose through the blue-grey haze, its tip outlined in
ruddy gold by the last of the setting sun.

Page 51

The mining ship was an ugly thing, sullen, entirely
practical. Its belly was studded with unconcealed grap-
plers, lifters, cutters, churners. If the master of this craft so
desired, its engines could easily convert all of Djamonkin
Crater into a steaming tornado of whirling rock and ore, sift-
ing, lifting and storing whatever components it wished to
carry back.

Technological capabilities capabilities:

Page 100

From those inner secrets, the Forerunners have
prodded sufficient power to change the shape of worlds,
move stars, and even to contemplate shifting the axes of
entire galaxies. We have explored other realities, other
spaces – slipspace, denial of locale, shunspace, trick geo-
detics, natal void, the photon-only realm the Glow.

Page 143-144

The sensor images were impressive and strange. I had
never seen a quarantined steller system before. Such capa-
bilities were rarely displayed to young Builders. A planetary
system is mostly empty, even the greatest of worlds being lost

- page 144 -

in the immensity of billions of kilometers of space. Like their
former human allies, the San’Shyuum had evolved on a
water-rich world not far from a yellow star, within a temper-
ate zone that allowed only a narrow range of weather. Now,
however, ten thousand years after their defeat, the system
was surround by trillions of vigilants that constantly wove
in and out of space-time, sometimes so rapidly that they
seemed to shape a soild sphere. This sphere extended to a
distance of four hundred million kilometers from the star,
and thus did not encompass four impressive gas giants whose
orbit lay beyond that limit.

Page 145

“They retired the Deep Reverence here,” he murmured.
A magnified image appeared and was enhanced by specifi-
cations and other data. The Deep Reverence was an impres-
sive fortress-class vessel, fifty kilometers in length, its incept
data before the human-San’Shyuum war.

Firepower:

Page 197

The atmosphere below was a swirling soup of smoke and
fire. Warrior craft and automated weapon systems were
mostly to small to be visible, but I saw their effects – darting
beams of needle light, glowing arcs cutting across conti-
nents, gigantic, stamplike divots punched into the crust and
then lifted up, spun about, overturned. I had never seen
anything like this – but the Didact had.

FTL Speed:

Page 99

The display tracked our course. We were moving out-
ward along the great spiral arm that held both the Orion
complex and Erde-Tyrene – just a few tens of thousands of
light-years.

Hours at most would pass for us.

Page 134

HOURS LATER, WE emerged. The effects passed more
slowly than usual, indicating we had gone a very
great distance indeed, perhaps beyond the range of
normal particle reconciliation. There might be dilation ef-
fects when we returned.

I stood alone in the command center, looking out across
the tremendous, dim whirlpool of a galaxy, and called up a
chart to see where we were. Spirals and grids spread quickly.
At least this was our home galaxy. The ship was in a long,
obscure orbit, high above the galactic plane, tens of thou-
sands of light years from any feasible destination.

Four cruisers have sufficient firepower to shatter a Halo:

Halo: Cryptum page 314

The first fortress’s fighters moved in, surrounding one of the primed Halos and engaging its sentinels. Simultaneously, four cruisers sent white-hot beams to points around the targeted installation. Sentinels intercepted some of those beams, partially deflecting them but also absorbing and sacrificing. Other beams struck home, carving canyonlike gouges across the mottled inner surface and blowing blue-white plumes of debris and plasma from the edges. The interior spokes began to shimmer and fade. The Halo could not hold together against this onslaught. It bent inward, wobbled. Fascinated, I watched as huge sections of the ring twisted like ribbon, giving way to destructive nodes of resonance, then rippled in sinus waves—and separated with agonizing majesty.

Who wins?

[Norade]

Pages 11 and 51

Twenty kilometers away, the central peak of Djamonkin
Crater rose through the blue-grey haze, its tip outlined in
ruddy gold by the last of the setting sun.

Page 51

The mining ship was an ugly thing, sullen, entirely
practical. Its belly was studded with unconcealed grap-
plers, lifters, cutters, churners. If the master of this craft so
desired, its engines could easily convert all of Djamonkin
Crater into a steaming tornado of whirling rock and ore, sift-
ing, lifting and storing whatever components it wished to
carry back.

The ability to mine should be equal as we've seen that Star Wars can build things like World Devastators which can mine and produce new ships very quickly.

Page 100

From those inner secrets, the Forerunners have
prodded sufficient power to change the shape of worlds,
move stars, and even to contemplate shifting the axes of
entire galaxies. We have explored other realities, other
spaces – slipspace, denial of locale, shunspace, trick geo-
detics, natal void, the photon-only realm the Glow.

We know that Star Wars can move planet sized objects at least, though they've never moved a star outside of the builders of Centerpoint station. As for contemplating shift the axis of a galaxy, well, we don't know how seriously they considered it nor the time frame for doing so. As for the rest Star Wars also uses other dimensions for travel and things as mundane as fuel storage.

Page 143-144

The sensor images were impressive and strange. I had
never seen a quarantined steller system before. Such capa-
bilities were rarely displayed to young Builders. A planetary
system is mostly empty, even the greatest of worlds being lost

- page 144 -

in the immensity of billions of kilometers of space. Like their
former human allies, the San’Shyuum had evolved on a
water-rich world not far from a yellow star, within a temper-
ate zone that allowed only a narrow range of weather. Now,
however, ten thousand years after their defeat, the system
was surround by trillions of vigilants that constantly wove
in and out of space-time, sometimes so rapidly that they
seemed to shape a soild sphere. This sphere extended to a
distance of four hundred million kilometers from the star,
and thus did not encompass four impressive gas giants whose
orbit lay beyond that limit.

Sounds like they mined out a system here and then went overboard on blockading it. Really nothing special aside from the resources wasted blocking it off.

Page 145

“They retired the Deep Reverence here,” he murmured.
A magnified image appeared and was enhanced by specifi-
cations and other data. The Deep Reverence was an impres-
sive fortress-class vessel, fifty kilometers in length, its incept
data before the human-San’Shyuum war.

That size is large, but we know Star Wars can match.

Page 197

The atmosphere below was a swirling soup of smoke and
fire. Warrior craft and automated weapon systems were
mostly to small to be visible, but I saw their effects – darting
beams of needle light, glowing arcs cutting across conti-
nents, gigantic, stamplike divots punched into the crust and
then lifted up, spun about, overturned. I had never seen
anything like this – but the Didact had.

That tells us next to nothing about firepower and that description could as easily apply to a Star Destroyer attacking a planet.

Page 99

The display tracked our course. We were moving out-
ward along the great spiral arm that held both the Orion
complex and Erde-Tyrene – just a few tens of thousands of
light-years.

Hours at most would pass for us.

Sounds like hours for them, but that would only be due to time dilation to an unknown degree. So hard to say anything from this.

Page 134

HOURS LATER, WE emerged. The effects passed more
slowly than usual, indicating we had gone a very
great distance indeed, perhaps beyond the range of
normal particle reconciliation. There might be dilation ef-
fects when we returned.

I stood alone in the command center, looking out across
the tremendous, dim whirlpool of a galaxy, and called up a
chart to see where we were. Spirals and grids spread quickly.
At least this was our home galaxy. The ship was in a long,
obscure orbit, high above the galactic plane, tens of thou-
sands of light years from any feasible destination.

Again, hard to say.

Halo: Cryptum page 314

The first fortress’s fighters moved in, surrounding one of the primed Halos and engaging its sentinels. Simultaneously, four cruisers sent white-hot beams to points around the targeted installation. Sentinels intercepted some of those beams, partially deflecting them but also absorbing and sacrificing. Other beams struck home, carving canyonlike gouges across the mottled inner surface and blowing blue-white plumes of debris and plasma from the edges. The interior spokes began to shimmer and fade. The Halo could not hold together against this onslaught. It bent inward, wobbled. Fascinated, I watched as huge sections of the ring twisted like ribbon, giving way to destructive nodes of resonance, then rippled in sinus waves—and separated with agonizing majesty.

Sounds impressive, but a single ship exploding did the same so it's really nothing too amazing.

Who wins?

I'm going to say that we don't know enough about the forerunners to call this. Though they did lose to weak sauce space zombies so we know they're dumber than a post.

[Eulogy]

I'm going to say that we don't know enough about the forerunners to call this. Though they did lose to weak sauce space zombies so we know they're dumber than a post.

Which raises the question of how they were able to get into space in the first place, never mind building all the Haloes and various other toys. Stupid races don't build starships, they get eaten.

[ChosenOne54]

I'm going to say that we don't know enough about the forerunners to call this. Though they did lose to weak sauce space zombies so we know they're dumber than a post.

I'm not going to call a winner either, but this isn't particularly accurate. The Forerunners were slow to see the threat, due to some stupidity, but by the final years of the war, not only did their most advanced AI, Mendicant Bias, holding a large portion of the fleet betray them, but the Flood had evolved so much as to have assimilated entire fleets as well. The Flood essentially used their technology against them; they were fighting their own technology, backed by their own most intelligent AI, and the Gravemind, who was coordinating the attacks.

[Norade]

I'm going to say that we don't know enough about the forerunners to call this. Though they did lose to weak sauce space zombies so we know they're dumber than a post.

I'm not going to call a winner either, but this isn't particularly accurate. The Forerunners were slow to see the threat, due to some stupidity, but by the final years of the war, not only did their most advanced AI, Mendicant Bias, holding a large portion of the fleet betray them, but the Flood had evolved so much as to have assimilated entire fleets as well. The Flood essentially used their technology against them; they were fighting their own technology, backed by their own most intelligent AI, and the Gravemind, who was coordinating the attacks.

Doesn't change the fact that the flood can be brought down by today's weapons and should have been contained earlier one. That they were able to have their best AI convinced to leave them shows either that they were a fading power anyway, or that they have poor computer security. Oh wait, we're supposed to believe that the gravemind can telepathically hack AI just because now.

[ChosenOne54]

The Flood Forms you see in the Halo games I would assume were vastly inferior. The form the Forerunners were facing was consuming entire solar systems, forcing the Forerunners to kersplode suns, and even that didn't stop the advance. I don't know too much on the topic of Mendicant and the Gravemind though.

[lordofchange13]

The Flood Forms you see in the Halo games I would assume were vastly inferior. The form the Forerunners were facing was consuming entire solar systems, forcing the Forerunners to kersplode suns, and even that didn't stop the advance. I don't know too much on the topic of Mendicant and the Gravemind though.

While the flood ate entire solar systems, the forerunners had an entire galaxy of resources and soldiers to call upon; as well (if the forerunner trilogy is canon) as well seasoned army that on multiple occasions exterminated whole civilations and subjagated there peoples (humans). they failed from the start: they belived there ultratech guns were invincible that they didn’t even virus scan the AI they put in command of there entire fleet. While a relatively crude race of space faring humans was able to fend off the flood, the humans being militarily weaker, lower tech, and having a lower manufacturing base to supply there war. And to answer the thread: the Star Wars Empire’s military and manufacturing ability are massively greater then the forerunners before and after the Flood

[Srelex]

Perhaps we'll have to see how the Flood are depicted in the upcoming Forerunner books--given that the author rather upped the Forerunners from what we saw before (e.g. Legends) it remains to be seen what he'll do the Flood.

[ChosenOne54]

And to answer the thread: the Star Wars Empire’s military and manufacturing ability are massively greater then the forerunners before and after the Flood

Eh? This was the area that I thought would be extremely in the favour of the Forerunners. The Forerunners build worlds, literally. The Ark is 127,530km in diameter, and is capable of producing an entire Halo in months. The Forerunner capital is 100 000 km in diameter, sliced horizontally with cities in between (if I'm interpreting the quote correctly). They have built micro dyson spheres with a diameter of 300 million kilometers, folded up in a slipspace bubble.

Hell, standard Forerunner capital ships, the Fortress Class vessel (http://www.halopedian.com/Fortress-class_vessel), ranges from 50 to 100km in length, almost as big as the Death Star. And it's just a warship; not a space station, not even particularly large by Forerunner standards, capable of releasing hundreds, possibly even thousands of cruisers and fighters. It's practically a fleet on its own.

[Solauren]

How well will the Forerunners fare against
- the Death Star? (or Death Star II)
- World Devestators
- the Sun Crusher (a star fighter that can take full power shots from the Death Star's super laser, and can cause any star to go SUPER NOVA)
- the Galaxy Gun

[Srelex]

Technically speaking the Empire had none of that at the height of it's power, which I take to be about ANH.

[ChosenOne54]

- the Death Star? (or Death Star II)

Standard Forerunner ships can devastate planets and shatter Halos as is. The fact that the Empire requires a massive space station to destroy planets says something. And yes, I know they have Base Delta Zero, that is just slagging the surface of a planet if I am not mistaken.

- the Sun Crusher (a star fighter that can take full power shots from the Death Star's super laser, and can cause any star to go SUPER NOVA)

Blowing up suns was standard procedure during the war against the Flood. Basically the same as above.

[Sarevok]

Standard Forerunner ships can devastate planets and shatter Halos as is. The fact that the Empire requires a massive space station to destroy planets says something. And yes, I know they have Base Delta Zero, that is just slagging the surface of a planet if I am not mistaken.

Forerunner ships can mass scatter planets similar to Death Star ?

Blowing up suns was standard procedure during the war against the Flood. Basically the same as above.

And yet they lost to a bunch of zombies.

A bunch of zombies with no industry capable of producing their own ships and weapon.

With that kind of tactical acumen the Forerunners could be given all the weapons technology found on a Culture ship and still lose to the Empire.

[ChosenOne54]

Forerunner ships can mass scatter planets similar to Death Star ?

Four Forerunner cruisers shattered a Halo.

And yet they lost to a bunch of zombies.

A bunch of zombies with no industry capable of producing their own ships and weapon.

With that kind of tactical acumen the Forerunners could be given all the weapons technology found on a Culture ship and still lose to the Empire.

The Flood started out as a disease; some unhealthy fur growth in animals. The Forerunners treated it accordingly. Only later did they realize their mistake, and treat it like a war, by which time their most advanced AI, controlling a large portion of their fleet betrayed them. With the Galactic Empire, they would make no such mistake; the Empire has a fleet, and they are mostly human. The Forerunners would recognize them as an enemy straightaway and declare war.

[Norade]

Forerunner ships can mass scatter planets similar to Death Star ?

Four Forerunner cruisers shattered a Halo.

That means little given that a single exploding ship did the same.

And yet they lost to a bunch of zombies.

A bunch of zombies with no industry capable of producing their own ships and weapon.

With that kind of tactical acumen the Forerunners could be given all the weapons technology found on a Culture ship and still lose to the Empire.

The Flood started out as a disease; some unhealthy fur growth in animals. The Forerunners treated it accordingly. Only later did they realize their mistake, and treat it like a war, by which time their most advanced AI, controlling a large portion of their fleet betrayed them. With the Galactic Empire, they would make no such mistake; the Empire has a fleet, and they are mostly human. The Forerunners would recognize them as an enemy straightaway and declare war.

They might not if the Empire were to bide its time and prepare things before attacking. They could even trade for forerunner tech first. People tend toforget that war isn't just mashing forces together.

[ChosenOne54]

That means little given that a single exploding ship did the same.

Here is a more detailed quote just for reference:

Halo Cryptum pg 320
Even before it had emerged halfway,the fortress began to loose clouds of fighters-at this distancenthey resembled a puff of pollen from a flower-and fire it's weapons in a sequential radiance.The inner curve of the Halo,even protected by waves of hard light,could not stand up long to this assault from within it's own radius.
The fortress's commanders and ancillas must have known they were dooming themself as well as the Halo.The installation began a spectacular disintegrative sequence.The visible half of the ring bent in opposite directions,then shattered into five great arc.

Not only is this ring protected by hard light (unfortunately I can't quantify it's power, but it must have had some effect), but this ring was much larger than the one in Halo. 3 times, in fact (this one is 30 000 km, the one in halo was only 10 000 kilometres in diameter).
http://www.halopedian.com/Halo_Array#Technology

They might not if the Empire were to bide its time and prepare things before attacking. They could even trade for forerunner tech first. People tend toforget that war isn't just mashing forces together.

I'm pretty sure this thread is an all-out war, maybe the OP should specify.

[Norade]

That means little given that a single exploding ship did the same.

Here is a more detailed quote just for reference:

Halo Cryptum pg 320
Even before it had emerged halfway,the fortress began to loose clouds of fighters-at this distancenthey resembled a puff of pollen from a flower-and fire it's weapons in a sequential radiance.The inner curve of the Halo,even protected by waves of hard light,could not stand up long to this assault from within it's own radius.
The fortress's commanders and ancillas must have known they were dooming themself as well as the Halo.The installation began a spectacular disintegrative sequence.The visible half of the ring bent in opposite directions,then shattered into five great arc.

Not only is this ring protected by hard light (unfortunately I can't quantify it's power, but it must have had some effect), but this ring was much larger than the one in Halo. 3 times, in fact (this one is 30 000 km, the one in halo was only 10 000 kilometres in diameter).
http://www.halopedian.com/Halo_Array#Technology

So it had shields of unknown magnitude and was killed by a few ships. We still know nothing. If it was just as thick as the ring from the game then it was only a few kilometers thick and we know Star Wars can burn down that deep with a BDZ, we can also assume that breaking the ring in certain places will cause strain that will help the ring to break itself apart.

They might not if the Empire were to bide its time and prepare things before attacking. They could even trade for forerunner tech first. People tend toforget that war isn't just mashing forces together.

I'm pretty sure this thread is an all-out war, maybe the OP should specify.

Need an all out war happen straight away? Besides, you can't just fiat that one side bum rushes in without doing the steps they should logically take.

[ChosenOne54]

So it had shields of unknown magnitude and was killed by a few ships. We still know nothing. If it was just as thick as the ring from the game then it was only a few kilometers thick and we know Star Wars can burn down that deep with a BDZ, we can also assume that breaking the ring in certain places will cause strain that will help the ring to break itself apart.

The destruction of the ring in Halo was more of a chain reaction than anything else. The explosion caused some pieces to break off, one of them impacting the other side causing it to break apart as well. In the quote I provided, the ships pretty much brute force the ring, shattering it into five pieces. These are the weapons equipped on their fighters.

Need an all out war happen straight away? Besides, you can't just fiat that one side bum rushes in without doing the steps they should logically take.

I doubt trading of technology would happen in an all out war, but again, the OP should specify.

[Norade]

So it had shields of unknown magnitude and was killed by a few ships. We still know nothing. If it was just as thick as the ring from the game then it was only a few kilometers thick and we know Star Wars can burn down that deep with a BDZ, we can also assume that breaking the ring in certain places will cause strain that will help the ring to break itself apart.

The destruction of the ring in Halo was more of a chain reaction than anything else. The explosion caused some pieces to break off, one of them impacting the other side causing it to break apart as well. In the quote I provided, the ships pretty much brute force the ring, shattering it into five pieces. These are the weapons equipped on their fighters.

Give me enough fighters and I'll blow up anything. If they were really like 'a puff of pollen from a flower' that could mean thousands of fighters at least. With Star Wars level weapons that could mean anything from a few megatons a second from laser only to

Need an all out war happen straight away? Besides, you can't just fiat that one side bum rushes in without doing the steps they should logically take.

I doubt trading of technology would happen in an all out war, but again, the OP should specify.

Who jumps blindly into an all out war? Certainly not the empire we see in canon, not against a complete unknown.

[ChosenOne54]

Give me enough fighters and I'll blow up anything. If they were really like 'a puff of pollen from a flower' that could mean thousands of fighters at least. With Star Wars level weapons that could mean anything from a few megatons a second from laser only to

There's also an example of the OP of four cruisers doing pretty much the same thing. And it's not like the Forerunners have any shortage of fighters or cruisers anyway. I can't imagine just how many ships could be crammed into a 14km Forerunner Dreadnought leave alone a 100km Forerunner Fortress Class vessel, which is practically a fleet on its own.

Who jumps blindly into an all out war? Certainly not the empire we see in canon, not against a complete unknown.

Trading technology with a faction they are about to fight still seems rather unlikely to me. What kind of tactics would they use? Because from what I understand of the OP, he basically put two armies against each other and said "fight."

[Norade]

Give me enough fighters and I'll blow up anything. If they were really like 'a puff of pollen from a flower' that could mean thousands of fighters at least. With Star Wars level weapons that could mean anything from a few megatons a second from laser only to

There's also an example of the OP of four cruisers doing pretty much the same thing. And it's not like the Forerunners have any shortage of fighters or cruisers anyway. I can't imagine just how many ships could be crammed into a 14km Forerunner Dreadnought leave alone a 100km Forerunner Fortress Class vessel, which is practically a fleet on its own.

How large is a cruiser? How many do they have? For all we know they have less numerous larger ships and they get swarmed by ISD's.

Who jumps blindly into an all out war? Certainly not the empire we see in canon, not against a complete unknown.

Trading technology with a faction they are about to fight still seems rather unlikely to me. What kind of tactics would they use? Because from what I understand of the OP, he basically put two armies against each other and said "fight."

Why would you assume the new galaxy you just discovered would be instantly hostile to you? Even if they did go to war it's doubtless that the two sides would communicate first.

[Jake1]

That means little given that a single exploding ship did the same.

That single exploding ship had a thermal radiation radius equal to the diameter of the halo (10,000km). From the nuclear explosion calculator on this page that gives a total energy of about 6E22 joules or 1.426E7 megatons.

[ChosenOne54]

How large is a cruiser? How many do they have? For all we know they have less numerous larger ships and they get swarmed by ISD's.

We don't have an exact number, but we can estimate about how many they have based of quotes from the Halo 3 Terminals:

In support of 05-032's original 1000 core vessels is a fleet numbering 4,802,019; though only 1.8 percent are warships - and only 2.4 percent of that number are capital ships - I am outnumbered [436.6:1]. I expect my losses will be near total, but overwhelming force has its own peculiar drawbacks.

In this quote, it is said that Mendicant Bias had a fleet of about 4 802 019 ships, 1.8% of those being warships. So doing the math, you get about 86 436 warships under the control of Mendicant Bias alone. Of that percentage, 2.4% are capital ships, so again, doing the math bring us to about 2074 capital ships. We don't exactly know how many, but 'capital ship' probably includes Dreadnoughts and Fortress Class vessels.

Then we add in the number of ships Offensive Bias had under his command. He states he is outnumbered 436.6 to one, and assuming all of Offensive’s ships are military vessels (he was designed specifically to combat Mendicant), that gives him about 10 998 ships.

Add the fleets of Mendicant and Offensive Bias together and you get roughly 97 434 warships. That likely isn't the entire fleet, as the events of the terminal are very late into the war anyway.

Unless I screwed up and fail at math

Why would you assume the new galaxy you just discovered would be instantly hostile to you? Even if they did go to war it's doubtless that the two sides would communicate first.

Uh, this IS a vs. debate, not a scenario of the Galactic Empire negotiating with the Forerunners of anything to that effect.

[Norade]

How large is a cruiser? How many do they have? For all we know they have less numerous larger ships and they get swarmed by ISD's.

We don't have an exact number, but we can estimate about how many they have based of quotes from the Halo 3 Terminals:

In support of 05-032's original 1000 core vessels is a fleet numbering 4,802,019; though only 1.8 percent are warships - and only 2.4 percent of that number are capital ships - I am outnumbered [436.6:1]. I expect my losses will be near total, but overwhelming force has its own peculiar drawbacks.

In this quote, it is said that Mendicant Bias had a fleet of about 4 802 019 ships, 1.8% of those being warships. So doing the math, you get about 86 436 warships under the control of Mendicant Bias alone. Of that percentage, 2.4% are capital ships, so again, doing the math bring us to about 2074 capital ships. We don't exactly know how many, but 'capital ship' probably includes Dreadnoughts and Fortress Class vessels.

Then we add in the number of ships Offensive Bias had under his command. He states he is outnumbered 436.6 to one, and assuming all of Offensive’s ships are military vessels (he was designed specifically to combat Mendicant), that gives him about 10 998 ships.

Add the fleets of Mendicant and Offensive Bias together and you get roughly 97 434 warships. That likely isn't the entire fleet, as the events of the terminal are very late into the war anyway.

Unless I screwed up and fail at math

Okay, so that's all well and good without us knowing how they define things. The Empire has at least 25,000 ISD's as well as both larger and smaller support vessels. Publius had some good data on the overall state of Star Wars fleet counts and he came up with number of 24 ISD's per sector fleet with ~1,600 other combat craft meaning that at the low end we would have 25,000 ISD's and 1,665,600 other combat craft just from sector groups. Toss in ships that don't fit into these groups and that number gets much large. Add in warships that protect Imperial worlds that aren't part of Imperial fleets and... well you get the picture. In a pure force on force action

Even granting the forerunners an extra 50% fleet strength, which doesn't always make sense because late in a war would would expect to see the largest fleets in many cases, you would only get ~3,500 fore runner capital ships and ~145,000 other combatants. This marks capital ships as being outnumbered 7:1 by ISD's and the other ships by at least 11:1.

Why would you assume the new galaxy you just discovered would be instantly hostile to you? Even if they did go to war it's doubtless that the two sides would communicate first.

Uh, this IS a vs. debate, not a scenario of the Galactic Empire negotiating with the Forerunners of anything to that effect.

You can't just ignore how each side has been known to act when doing such things.

[ChosenOne54]

Okay, so that's all well and good without us knowing how they define things. The Empire has at least 25,000 ISD's as well as both larger and smaller support vessels. Publius had some good data on the overall state of Star Wars fleet counts and he came up with number of 24 ISD's per sector fleet with ~1,600 other combat craft meaning that at the low end we would have 25,000 ISD's and 1,665,600 other combat craft just from sector groups. Toss in ships that don't fit into these groups and that number gets much large. Add in warships that protect Imperial worlds that aren't part of Imperial fleets and... well you get the picture. In a pure force on force action

Even granting the forerunners an extra 50% fleet strength, which doesn't always make sense because late in a war would would expect to see the largest fleets in many cases, you would only get ~3,500 fore runner capital ships and ~145,000 other combatants. This marks capital ships as being outnumbered 7:1 by ISD's and the other ships by at least 11:1.

Hm, well there's nothing I can say to that. As you said, we don't have a ton of information on the Forerunner's capabilities. I guess we'll have to wait until the next book is released, or passibly the next game.