I was just sitting in a conference during a rather boring speaker and I can't stop thinking about that. Is it Millions? Billions?

To clarify, I'm looking for the number of fulltime rebellion personnel, not sympathisants. One of the ways we could guestimate the number is the

1. Battle of yavin. I think it was mentioned in a book how many people the base was built for, and since it was the mainbase (something the rebellion tried not to replicate by spreading the fleet accros several bases). Also, I think we can all agree that most capable starfighter pilots the rebellion had access to were thrown into that fight. Yes, several might have been away on mission, but as I said, we're guestimating.
2. Battle of Hoth. Also a mainbase, but at this point the rebellion is spread out much more. Still, I believe we see how many Transporters are leaving the base and have a general idea how many beings you can fit on one of those.
3. Battle of Endor. As far as I know the Rebellion threw every ship and everything else that goes vrooom and pew pew into that battle. Do we know how many ships of what type were present?

I will gladly assist in research to find a satisfying estimate, but currently I'm sitting in a huge hall with several thousand people, which makes the wifi annoyingly slow.

Secondly, I have to shamefully admit, that there are people who know more about star wars than me Maybe there is an estimate given somewhere in a behind the scenes book.

I'd be happy if we manage a minimum number that we can guarantee from the movies.

Anybody interested in this, undertaking?

Guessing the Bothan deathtoll must be in the millions alone.

Overall? Safe to say it's in the millions, as the battles and major military conflicts we see in the films are only a slice of what was happening elsewhere. Although the canon events are also among the larger-scale events, meaning that other actions are smaller acts of espionage or skirmishes with smaller groups. If you take into consideration that for every X-Wing pilot there are likely 20 people behind the scenes, doing logistics, repair, coordination, etc, then the number of people start to jump dramatically. And those people would be "fulltime", according to your definition.

According to Wookieepedia, the battle of Yavin 4 had 30 rebel starfighters (and 1 freighter) taking part.

That's roughly 30-38 pilots (depending on how many Y-wings were one-man or two-man configurations).

I'd say that at that point the Rebel Alliance was in its infancy stages.
Judging from the tv-show Rebels, it's actually quite plausible that there were many different rebel factions and this simply was the largest one at that time.

The battle of Endor, however, shows a vast increase in the size of the rebellion.

The rebel fleet (again according to wookieepedia) was comprised of several capitol ships with crews in the hundreds, in some cases thousands.

We know that at least two mon calamari starcruisers were destroyed, and that the one that admiral akbar was on survived.
So there's 15.000 in crew alone, right there.

Add to that the numerous corellian corvettes and nebulon-b frigates, and all of the different starfighters, I'd say we're looking at a force of at the very minimum 30.000 combattants.

And that's just in space.
There's also the commando troops on the ground.

But I'm guessing that the force was actually larger than that, it's just that the limitations of movie production means we only see part of it.

The Imperial fleet, however, consisted of more than a million crewmembers on the various star destroyers (I counted at least 21 "regular" imperial class star destroyers in the picture from inside the cockpit of the milennium falcon on wookieepedia)

There's plenty of historical examples to pull from.

What we see in Ep 4 & 5 is definitely rag tag and on the run, so very small numbers. In Ep 6 the novelization talks about the fleet stretching beyond view or something, of course that's literary silliness in outer space, but leaves it wide open to whatever you like.

I'd say by Ep 6 the Rebellion with an 'all in' 'Hail Mary' effort can muster a fleet big enough for a stand up head to head battle over a system.

In the end it's open enough to be interpreted however fits best at anyone's table.

More or less the most applicable example from history imo.

"The French Resistance (French: La Résistance française) is the name used to denote the collection of French resistance movements that fought against the Nazi Germanoccupation of France and against the collaborationist Vichy régime during the Second World War. Résistance cells were small groups of armed men and women (called theMaquis in rural areas),^[2][3] who, in addition to their guerrilla warfare activities, were also publishers of underground newspapers, providers of first-hand intelligence information, and maintainers of escape networks that helped Allied soldiers and airmen trapped behind enemy lines. The men and women of the Résistance came from all economic levels and political leanings of French society, including émigrés; academics, students, aristocrats, conservative Roman Catholics (including priests) and also citizens from the ranks of liberals, anarchists and communists.

The French Resistance played a significant role in facilitating the Allies' rapid advance through France following the invasion of Normandy on 6 June 1944, and the lesser-known invasion of Provence on 15 August, by providing military intelligence on the German defences known as the Atlantic Wall and on Wehrmacht deployments and orders of battle. The Résistance also planned, coordinated, and executed acts of sabotage on the electrical power grid, transport facilities, and telecommunications networks.^[4][5] It was also politically and morally important to France, both during the German occupation and for decades afterward, because it provided the country with an inspiring example of the patriotic fulfillment of a national imperative, countering an existential threat to French nationhood. The actions of the Résistance stood in marked contrast to thecollaboration of the French regime based at Vichy,^[6][7] the French people who joined the pro-Nazi milice and the French men who joined the Waffen SS.

After the landings in Normandy and Provence, the paramilitary components of the Résistance were organised more formally, into a hierarchy of operational units known, collectively, as the French Forces of the Interior (FFI). Estimated to have a strength of 100,000 in June 1944, the FFI grew rapidly and reached approximately 400,000 by October of that year.^[8] Although the amalgamation of the FFI was, in some cases, fraught with political difficulties, it was ultimately successful, and it allowed France to rebuild the fourth-largest army in the European theatre (1.2 million men) by VE Day in May 1945.^[9]"

I doubt there are 20 pogs for every fighter jock or grunt. The modern US army is pretty bloated with non-combat arms personnel, and I think they're sitting somewhere around a 10:1 or 7:1 ratio right now. A decade ago it was right around 10:1. The US Marine Corps is a bit more slim in this regard, and I doubt they've done better than 5:1 at any point since WWII.

Hoth: Headquarters =/= majority of personnel and equipment are there. Just that that's where the top leadership is, as well as enough troops/equipment/vehicles to protect them. Again, I can't see Star Wars being radically different from modern day in that regard. So as a for instance, 7th Fleet Headquarters is, IIRC, Pearl Harbor, Hawaii, but the US Navy hasn't had the majority of its ships in port there since December of 1941. Marine Corps headquarters is Quantico, Virginia, but the nearest major combat unit concentration is Camp Lejeune. So I'd think that the Rebellion would have maybe a division of infantry on Hoth, though more likely just a regiment. Plus all the clerks, techs, mechanics, pilots, command staff. Remember, these people need to eat, need medical supplies, parts for machines, etc, and everything has to come from somewhere else. The more people there, the more stuff they need, so the more often transports have to take off/land. Which increases the chance of discovery.

Endor: The rebels thought they were getting the drop in the Empire, and they knew how to destroy the Death Star. They obviously didn't expect the Empire to have a huge fleet assembled, so it stands to reason that they wouldn't have brought their entire fleet. And, just in case they lost the battle, it would make sense to leave other forces to carry on the fight.

There are probably tens of trillions of sentients in the galaxy. Coruscant alone has what, 22 billion or something crazy like that, according to the AoR and EotE books? I think it's reasonable to estimate the total manpower of the Rebellion in the millions, perhaps tens of millions. That may sound like a lot but compared to the Galactic Population, it's not. It's like comparing East BFE, Iowa to Tokyo or Mexico City.

I don't think that the rebels threw every fighter they had into the battle at Yavin. I think they threw the fighters that we're stationed there into the battle. In the movie, it didn't look like more than a few squadrons. And Han, Luke, Leia, and Chewbacca didn't know they'd been followed. They had some idea (Leia said the Empire let them escape), but if the rebels had known the Death Star was on the way, they'd have evacuated like they did at Hoth, where there was no Death Star. It seems more like they were surprised by the DS just showing up. So they briefed the pilots on how to kill it, sent them all out, and prayed.

I would say that in the Ep VI we see only the "main task force" of the rebel scum(m)s. If we follow the EU, there were plenty rebel cells around the galaxy fighting with their limited resources with acts of sabotage, guerrilla warfare, etc. The fleet battles happened before and after the Ep IV. And in case of Ep IV, there is not even the main task force, just one of their main bases, maybe the only one that Leia knows about at that moment. But even if we disregard the EU, remember this quote from the movie: "The Rebel Alliance is too well equipped. They're more dangerous than you realize." Could an Imperial general be preoccupied with a group that had roughly 30 starfighters?

There's plenty of historical examples to pull from.

What we see in Ep 4 & 5 is definitely rag tag and on the run, so very small numbers. In Ep 6 the novelization talks about the fleet stretching beyond view or something, of course that's literary silliness in outer space, but leaves it wide open to whatever you like.

I have a field of view that is only 180 degrees wide. So, even movie screens can stretch beyond my viewing. (which is one way for something to stretch beyond viewing).

A 1km long ship wouldn't be visible to the naked eye beyond about 5000km. Given that most of the rebel ships are smaller than that (most probably under the 200m size, making the limit down to only 1000km), then a fleet would easily stretch beyond viewing as real fleets couldn't be bunched up together as they'd need to be spaced apart to allow for maneuvering and to stay out of each other's engine exhaust. For example, a modern carrier battle group would be spread apart by as much as 100km from one edge to another making the distant elements very much over the horizon from the heart of the group.

For example, a modern carrier battle group would be spread apart by as much as 100km from one edge to another making the distant elements very much over the horizon from the heart of the group.

Yeah, well. One thing we know about Star Wars and the visual depiction of space and ships on screen is that what you see in the movies doesn’t typically have any relation whatsoever to what you would have in the “real” world.

If you can’t put two top-of-the-line Capital ships together close enough for the people to fistfight as they pass by, or to literally have a kitchen sink from one ship get blasted out and hit the other ship less than a second later, then it’s just not visually interesting enough.

I think it's safe to assume that the rebels only had sufficient strength at the battles of Yavin and Hoth to drive away any pirates that might decide to attack the rebels, to bushwhack Imperial reconnaissance ships, and to slow a full-on Imperial assault long enough to allow for most of the rebels - and primarily their leadership - to escape (at Hoth, the rebels pretty definitely left a significant portion of their infantry behind to be killed or captured). So any forces seen are going to be a small force, only sufficient to the task at hand - and in the case of Hoth, unlikely to be a force capable of repelling - or even slowing down - the sort of assault that Vader's Death Squadron was capable of unleashing.

I also think it's pretty safe to assume that not the entire Rebel fleet was engaged in the Battle of Endor, but probably the larger portion of it. Of course, the battle needed to be (for story purposes) something where the rebels were all in - and therefore to represent a significant enough portion of the rebel fleet that their destruction would effectively cripple the rebellion, particularly in combination with the completion of the Second Death Star. However, it makes logical military sense that significant portions of the rebel fleet and ground forces would be striking hard and fast against a variety of Imperial targets in an effort to draw the Imperial fleet away from the Second Death Star and keep them from reinforcing Imperial forces on and around Endor.

However, even if we assume that the fleet engaged in the battle of Endor represent at least 50% of the rebel's regular forces, it will only represent their regular fleet. While it is probable that the rebel fleet at Endor did carry a small contingent of marines or soldiers to reinforce or help withdraw the commandos on Endor, there is little reason for the fleet to have had many ground-pounders on board. Further, it is probably a safe assumption that irregular forces provide the largest portion of rebel combat strength, in the form of privateers, guerrillas, saboteurs, and spies. Groups like the Ghost and her crew likely serve as the backbone of the rebellion: Regular freighters and transport craft, common throughout the galaxy and thus unlikely to draw anyone's eyes, and capable of undertaking a wide variety of missions from piracy to intelligence gathering to acting as a simple courier (carrying intelligence or sensitive messages, exfiltrating or infiltrating spies or saboteurs, carrying rebel strike teams, &c.). Odds are that ships like the Ghost were very, very busy during and immediately before the battle of Endor, but half a galaxy away from the battle itself.

So regular rebel forces might only number a few tens or hundreds of thousands spread across several hundred vessels and bases ranging from small SIGINT gathering outposts to larger HQs, from fighters and bulk cargo ships to large warships like the MC-80. But the irregulars probably number in the millions, consisting of hundreds of thousands of small teams or individuals operating largely independently, on their home planets or in tramp freighters wandering the spacelanes and backroads of the galaxy.

For example, a modern carrier battle group would be spread apart by as much as 100km from one edge to another making the distant elements very much over the horizon from the heart of the group.

Yeah, well. One thing we know about Star Wars and the visual depiction of space and ships on screen is that what you see in the movies doesn’t typically have any relation whatsoever to what you would have in the “real” world.

If you can’t put two top-of-the-line Capital ships together close enough for the people to fistfight as they pass by, or to literally have a kitchen sink from one ship get blasted out and hit the other ship less than a second later, then it’s just not visually interesting enough.

That would be reminiscent of battles of the line from the days of cannon and sail. Take it with a grain of salt, like ground fights where both sides are just chaotic intermingling of people from either side of a fight with no obvious front, flank, etc...

For example, a modern carrier battle group would be spread apart by as much as 100km from one edge to another making the distant elements very much over the horizon from the heart of the group.

Yeah, well. One thing we know about Star Wars and the visual depiction of space and ships on screen is that what you see in the movies doesn’t typically have any relation whatsoever to what you would have in the “real” world.

If you can’t put two top-of-the-line Capital ships together close enough for the people to fistfight as they pass by, or to literally have a kitchen sink from one ship get blasted out and hit the other ship less than a second later, then it’s just not visually interesting enough.

That would be reminiscent of battles of the line from the days of cannon and sail. Take it with a grain of salt, like ground fights where both sides are just chaotic intermingling of people from either side of a fight with no obvious front, flank, etc...

Space combat in Star Wars is pretty much a mixture of WWII airplanes and Golden Age of Sail capital ship combat, perhaps best illustrated by the Battle of Coruscant from the opening of Revenge of the Sith, where we see Venator-class Star Destroyers trading broadsides with Separatist warships.

As many as wanted or aa needed to tell your story.

For example, a modern carrier battle group would be spread apart by as much as 100km from one edge to another making the distant elements very much over the horizon from the heart of the group.

Yeah, well. One thing we know about Star Wars and the visual depiction of space and ships on screen is that what you see in the movies doesn’t typically have any relation whatsoever to what you would have in the “real” world.

If you can’t put two top-of-the-line Capital ships together close enough for the people to fistfight as they pass by, or to literally have a kitchen sink from one ship get blasted out and hit the other ship less than a second later, then it’s just not visually interesting enough.

That would be reminiscent of battles of the line from the days of cannon and sail. Take it with a grain of salt, like ground fights where both sides are just chaotic intermingling of people from either side of a fight with no obvious front, flank, etc...

Space combat in Star Wars is pretty much a mixture of WWII airplanes and Golden Age of Sail capital ship combat, perhaps best illustrated by the Battle of Coruscant from the opening of Revenge of the Sith, where we see Venator-class Star Destroyers trading broadsides with Separatist warships.

Yup. I've seen the behind the scenes stuff that ILM used way back in the day (75/76) for doing the Deathstar run and it was all footage captured from things like P51s and P38s. Which is why they seem to move so slowly and make maneuvers like you'd expect with an atmosphere present (banking, diving, etc...).