Conquering Britain

[Caiaphas]

Aside from notable examples like Caesar and the Normans, has there ever really been a contemporary power that had thr capability to invade and conquer all of Great Britain?

[Sea Skimmer]

The French and Spanish both could have done it at various times, but generally the slow speed of communications and the incredible problems of physically paying for the wars of the era, really until the 18th century, prevented it from ever happening or often being a serious risk. War is expensive, distance and seaborne transport, even over short distances, greatly multiply costs. When most of the population barely produces enough to sustain themselves let alone pay taxes its rather hard to think about doing more then attacking the nearest castle.

Its also worth noting that even at the time elaborate plans like the original Spanish Armada were questioned by generals and civilians of the time; if one was willing to accept a high degree of risk invading the British isles with nothing but small boats and a loot and pillage army made a damn lot of sense. The British never had a real defense against that sort of attack until the Napoleonic Wars either, when a huge number of gunboats, inshore warship and detached coastal batteries were constructed. A integrated sort of reverse Atlantic Wall system in fact.

Course the other thing is between the 1066 Norman invasion, which actually took several years to takeover England, and like 1530 or something the British were the ones constantly invading France anyway. The 100 years war was what it was because the Norman invasion led to a situation where a King in London could also be King of multiple countries in what is now western France. So the invasion risk was basically irrelevant in any rational scenario, even could anyone have afforded it.

[B5B7]

Another thing to consider is that William was not invading as an invader, but was considered by many in England as the legitimate king, so Hastings was basically a contest between two claimants to the throne, and once Harold was dead, the contest was decided.
This is different to a hostile invasion where there can be massive resistance from local rulers and the populace.
Sure, there was a lot of rebellions, but that was typical back then, no matter who was king, as England consisted of a large number of competing lords.
Also, as I recall Julius Caesar never invaded Britain, it was Claudius who succeeded.

[Lord Revan]

Another thing to consider is that William was not invading as an invader, but was considered by many in England as the legitimate king, so Hastings was basically a contest between two claimants to the throne, and once Harold was dead, the contest was decided.
This is different to a hostile invasion where there can be massive resistance from local rulers and the populace.
Sure, there was a lot of rebellions, but that was typical back then, no matter who was king, as England consisted of a large number of competing lords.
Also, as I recall Julius Caesar never invaded Britain, it was Claudius who succeeded.

Caesar did invave Britain to prevent them from support their allies in the south but he didn't establish any permanent present on the isles.

As for conquering the british isles, IIRC it wasn't so much a case of "we don't have the capability to do this" as it was "it's not worth the cost". Basically if they threw everything they got into a single minded conquest of Britain they could do it, but the cost of said conquest would be so high that it would end up a phyrric victory.

[Captain Seafort]

Aside from notable examples like Caesar and the Normans, has there ever really been a contemporary power that had thr capability to invade and conquer all of Great Britain?

In addition to the general references above, you also have the French in the early 13th century (got ashore, put King Louis of England on the throne, got chased out) and the Dutch (invaded successfully in 1688).

[LaCroix]

The Danes? They did a pretty good job of invading pretty much all but southern England once they stopped (Viking)raiding and started playing for keeps.

[Captain Seafort]

The Danes? They did a pretty good job of invading pretty much all but southern England once they stopped (Viking)raiding and started playing for keeps.

Indeed, and Canute the Great did even better.

[SpottedKitty]

The Danes? They did a pretty good job of invading pretty much all but southern England once they stopped (Viking)raiding and started playing for keeps.

<nod> They did such a good job, for a couple of hundred years half of England was called the Danelaw.

[Caiaphas]

I'm noting that basically all of the examples cited come from before the Industrial Revolution; are there any nations that could've successfully conquered Britain after they began to industrialize aside from perhaps post-WWII United States?

[CetaMan]

Possible pre-WW1 Germany would of been able to if it was just between the two countries. If Germany could somehow get its troops and forces across the channel without the Royal Navy completely screwing the attempt up.

[Elheru Aran]

The RN really is the big game changer. It started tooling up and becoming one of the more skilled and powerful navies in European waters during the Napoleonic wars, which were right at the start of the Industrial Revolution, and while there was something of a lull in the mid 1800s, the increase in colonial domains meant the UK had to build up its forces in order to protect naval access to those colonies. Without the RN, they still had the massive numbers of coastal fortifications that they built during the Napoleonic era, which would have made landings hairy.

So essentially after Napoleon, any invader would have had to first penetrate a powerful naval screen (if not warships, then a large number of coastal gunboats) then land under fire from those fortifications. Not an inviting prospect for anybody. Aircraft might change it... but we know what happens to paratroopers who drop into hostile territory and then don't get reinforced in time.

[LaCroix]

If the US had kept completely out of the war (That's where this scenario becomes unrealistic, right away...), or at least not joined against Germany, and the Germans hadn't meddled with Russia, Nazi Germany is a contender. The U-boats were placing Britain under under quite some economical stress, even with the US helping out blatantly. Given a long enough embargo and build up time, and no drain of men and equipment to the eastern front grinder, I'd see them capable of launching a successful invasion.

[Simon_Jester]

I'm noting that basically all of the examples cited come from before the Industrial Revolution; are there any nations that could've successfully conquered Britain after they began to industrialize aside from perhaps post-WWII United States?

Not without a buildup that the British would have (or did) observe and counter. As an example...

Possible pre-WW1 Germany would of been able to if it was just between the two countries. If Germany could somehow get its troops and forces across the channel without the Royal Navy completely screwing the attempt up.

See, the thing is, as Kaiser Wilhelm's Germany started building up the capacity to conceivably beat the Royal Navy in a sea battle and make an invasion possible, exactly that threat became the motivation behind a massive buildup and modernization of the Royal Navy. The British had an entire genre of "invasion literature" in those days, revolving around the threat of invading armies getting past the fleet.

If we assume the British aren't just going to passively sit there and wait to be invaded, then... really, prior to World War II there were no other military powers reliably capable of building up their amphibious and airborne capability to a level they couldn't counter. The Nazis tried and failed badly, for instance.

It's conceivable that in some hypothetical Random Alternate Reality where a major nation had literally nothing else to do, they could have mobilized that kind of force... but at that point we're so far out into the world of bad alternate history where people do things for unrecognizable pseudo-reasons that it's hard to talk rationally about outcomes.

The RN really is the big game changer. It started tooling up and becoming one of the more skilled and powerful navies in European waters during the Napoleonic wars, which were right at the start of the Industrial Revolution...

Uh... sort of? I'd place the cutoff point considerably before the Napoleonic Wars. The Royal Navy was pretty solidly established as an institution before that time, and performed just about as well in, say, the Seven Years' War of 1756-63. That said, your conclusion isn't wrong, just postdated a bit. And the fortifications you mention, those definitely date to the Napoleonic era.

[K. A. Pital]

Who could have invaded Britain successfully? Lots of factors to consider.

Say, post-WWII USSR, if it had nukes and Western Europe fell under Soviet influence to a greater degree than IRL. Could happen, could be botched, could initiate a nuclear war depending on British relations with the US.

Depends on what many industrial nations of Europe do.

Same with Germany in WWI or II. A lot depends on strategic alliances and decisions, and development of weapons.

[Sea Skimmer]

If the US had kept completely out of the war (That's where this scenario becomes unrealistic, right away...), or at least not joined against Germany, and the Germans hadn't meddled with Russia, Nazi Germany is a contender. The U-boats were placing Britain under under quite some economical stress, even with the US helping out blatantly. Given a long enough embargo and build up time, and no drain of men and equipment to the eastern front grinder, I'd see them capable of launching a successful invasion.

Doubtful because of how powerful British ground forces and fixed defenses would become, the task was far less a geographic problem then that of the Germans building and defending the Atlantic wall. Plus a successful enough blockade precludes the need for invasion, and indeed planning for an invasion would only slow down imposing a U-boat and air blockade because of all the material diversions involved. The diesel engines you need for LCTs for example could just as well go in submarines. This is no doubt why after Sealion was suspended German interest in the topic entirely evaporated, even though the invasion of Russia was only supposed to consume 1941.

Even then invasion isn't what I'd call realistic. Sccessful blockade would preclude the need for an invasion politically, because the UK would just be forced into surrendering on negotiated terms at some point. Meanwhile by the time a blockade could have ever worked without US involvement the UK would have had so many armored divisions built up that no plausible invasion could work. That's why when Sealion was cancelled the Germans also just stopped bothering with even token or long term planning, it was irrelevant to any long term goals even if one was operating on the belief that Russia would fall in six month.

Some real fundamental problems start to hit home if you want to invade a UK defended by late 1942 levels of ground forces, like a lack of port capacity between the Biscay coast and the mouth of the Sheldt to even hold the invasion shipping. This was a problem for the French and Spanish too, keeping in mind that while they had much smaller requirements many of the modern channel ports are entirely artificial and were utterly tiny or didn't exist in prior centuries. Mechanization far improved the ability of an army to land over beaches...but it also skyrocketed the bulk and weight required to be landed.

[Captain Seafort]

Uh... sort of? I'd place the cutoff point considerably before the Napoleonic Wars. The Royal Navy was pretty solidly established as an institution before that time, and performed just about as well in, say, the Seven Years' War of 1756-63. That said, your conclusion isn't wrong, just postdated a bit. And the fortifications you mention, those definitely date to the Napoleonic era.

I'd argue that even during the War of the Spanish Succession Britain was already an extremely tough nut to crack, and it could well also be argued that the Royal Navy's performance in the Seven Years War was more impressive than in the 93-14 Wars, given that the French Navy Hawke thumped at Quiberon Bay was a far tougher opponent than the one destroyed at the Nile and Trafalgar.

[Sea Skimmer]

]See, the thing is, as Kaiser Wilhelm's Germany started building up the capacity to conceivably beat the Royal Navy in a sea battle and make an invasion possible, exactly that threat became the motivation behind a massive buildup and modernization of the Royal Navy. The British had an entire genre of "invasion literature" in those days, revolving around the threat of invading armies getting past the fleet.

I think it useful to point out that one of the thing Lord Fisher advocated and actually half got built was a new generation of light forces specifically to oppose invasion even were the British battlefleet sunk or drawn overseas (though he'd rather have gotten rid of the battlefleet completely and spammed even more at various times) which is exactly why in 1914 the UK had nearly four times as many submarines as Germany and a comical advantage in first class destroyers.

Germany was lagging behind in battleship construction before WW1, but it lag in smaller vessels was much greater. Course the High Seas Fleet was almost entirely lacking in purpose or strategic direction anyway.

Uh... sort of? I'd place the cutoff point considerably before the Napoleonic Wars. The Royal Navy was pretty solidly established as an institution before that time, and performed just about as well in, say, the Seven Years' War of 1756-63. That said, your conclusion isn't wrong, just postdated a bit. And the fortifications you mention, those definitely date to the Napoleonic era.

1690 was the last time the invasion risk could have been really high without major alt history. All it would have taken is Tourville following up a victory he had already won, and for which many were critical of him at the time.

The Napoleonic Wars really did not in hindsight have a great risk of a French invasion, unless Napoleon tried the small boat method in isolation and just dared risk his entire army being wiped out at sea. The problem with that always was okay, risking the army for taking England is worth it. But the same Army, plus the moral implications to the French war effort, seriously risked loosing France to all its land enemies.

The crazy French building plan going on right till 1814 actually had some math chance of outbuilding the British....but the utter lack of trained French crews by that point, even the physical men to make bad crews in some cases (read about the French 'buildup' around Venice....) meant the hull count had seriously lost meaning. We are after all talking about a naval system which had abolished the career position of gunner!

[Sea Skimmer]

I'd argue that even during the War of the Spanish Succession Britain was already an extremely tough nut to crack, and it could well also be argued that the Royal Navy's performance in the Seven Years War was more impressive than in the 93-14 Wars, given that the French Navy Hawke thumped at Quiberon Bay was a far tougher opponent than the one destroyed at the Nile and Trafalgar.

Yeah in the Seven Year War the French and Spanish were probably a lot more credible threat then post 1793, and actually did deny the British total sea superiority for several years. The problem was part of the way they did that was by fighting all over the world, rather then concentrating for decisive control of the English channel which is the only point that matters as far as invasion is concerned. Quiberon Bay nerfed that threat pretty hard. It also helped lead to the French no longer fighting to win, but only fighting for survival to carry out escort tasks ect... which pretty much ensured they'd never make up ground. That they had so many fewer overseas bases, and that so many more had proven very vulnerable didn't help matters, fixed fortifications consumed lots and lots of money too.

This is also when you started to really see the crew skill gap open up and then be sustained, in no small part for economic reasons. The French overseas trade got more and more stressed, with less and less to defend, reducing naval funding in peacetime and meaning when a war broke out they had smaller and inferior cadres to build upon. The British always had problems with manning too, the but it was a relative thing, more of what they did have was in peacetime service, more of the population in peacetime was in the merchant marine.

[Patroklos]

Even then invasion isn't what I'd call realistic. Successful blockade would preclude the need for an invasion politically, because the UK would just be forced into surrendering on negotiated terms at some point. Meanwhile by the time a blockade could have ever worked without US involvement the UK would have had so many armored divisions built up that no plausible invasion could work. That's why when Sealion was cancelled the Germans also just stopped bothering with even token or long term planning, it was irrelevant to any long term goals even if one was operating on the belief that Russia would fall in six month.

If the blockade was successful, which means an eventual win by the Luftwaffe as well, then the UK would be essentially out of oil and gasoline. They have minimal local generation and even less refining capacity, and with a German air victory that operating at all seems unlikely. Britain's crude production values seem impressive on paper, but most of that took place in their overseas territories, which is irrelevant if we consider a successful blockade the likely scenario. Plus their reserves would be drained by whatever activities the RN and remaining RAF are doing.

I question the longevity of these armored forces in the field, even in a defensive role. We saw how effectively German armored forces operated when suffering restrictions that were probably less than we are talking about the British suffering here.

Also Britain only produced 45Kish armored vehicles during the war, including all of the war post 1942 period when the U-boat interdiction was vastly diminished and the German air interference with industry was approaching zero. Germany produced 345Kish in the same period (inflated a bit via production and confiscated material from occupied territory) under the massive industrial interference of allied bombing which won't be the case here. Unless the argument is that they just can't get that numerical advantage into play, the situation decidedly favors the Germans. Not just in armor.

I'd also point out that a victorious Luftwaffe renders the RN useless in preventing an invasion. The RN can't operate in any strength within the range of massed German ground based air forces who have at least supremacy over the channel areas, if not their entire operating range. They would be far too vulnerable. A German air victory relegates the RN irrelevant to invasion defense unless we are postulating a landing area well away from the channel. Which is exactly what happened in real life, the bulk of the RN was pushed into the north of the island while the Battle of Britain raged. As long as the Luftwaffe was operating in force out of France the RN really had no role within range of continental air bases with the exception of their own submarines and surgical carrier strikes. Any prolonged presence or large scale formation maneuver would just be chewed to bits. Anything the size of corvette or bigger would be air power fodder.

[Simon_Jester]

I'm not sure it's quite that simple, especially when you bear in mind that it can be cold-bloodedly worth writing off destroyers and cruisers on a one-way mission to repel or cripple an invasion fleet.

[Patroklos]

In this scenario they would have to be kept days steaming distance from the channel to avoid being bombed in port or at sea, and there is zero reason to think a Germany in this situation wouldn't know the second they started a sortie into the channel either via U-boat or shore based recon aircraft and concentrate their airpower (and Navy to some extent) to counter it.

This is just an outgrowth of aircraft displacing surface ship weaponry as the primary fighting power in naval warfare. Its just a quirk of geography that land based aircraft vice carriers can be applied to most of the relevant invasion avenues. And that those avenues are just so short given the channel, there really isn't much time to react.

The RNs best hope to interfere is to marshal any carrier aircraft for a strike at the invading fleet assuming anything remains from their loss in the Battle of Britain. This would still expose their fleet to German air attack but then the Germans would have to travel out to them to do so. Even then I doubt it would be enough to stop an invasion, and there is no reason the Germans couldn't provide adequate defensive air cover over their invasion force. Luftwaffe numbers to RN carrier aircraft numbers (being optimistic for the UK) are still ridiculously lopsided in favor of the Germans, and that's before you take into account the superiority of almost all Luftwaffe land based airframes to British carrier based airframes. And the Germans are operating from sprawling airbases just miles from the action, vice whatever distance the RN aircraft would have to travel to ensure their carriers have some distance from France to give them some protection.

[Alkaloid]

The problem with nearly all of these 'Sealion somehow works' scenarios is that no one ever talks about what Germany doesn't build to develop these capabilities.

Lets say Germany somehow builds enough U-Boats that the blockade is considered successful.

Historically, the German's ability to sink ships with aircraft was absolutely shit tier. At Dunkirk, where conditions were quite literally perfect for sinking ships with aircraft, the Luftwaffe managed to sink a grand total of 9 destroyers. I don't know if you've looked at the number of ships the RN had during world war 2, but 9 destroyers is quite literally fuck all by their standards. There were about 20 active Battleships in the RN at this point. But OK, let's imagine that Germany decide they want to have a good crack at this. First they need an air wing capable of hitting naval targets. In WW2 that's torpedo bombers, because dive bombers were OK at hitting carriers sometimes, and that's about it.

So the Luftwaffe needs to be massively larger, because for this plan to work it needs to develop and build and entire naval strike capability from scratch, as well as have the massive increase in fighters it needs to establish air superiority over Britain. Note that this still means aircraft operating from bases in Northen England can interfere with your torpedo bombers and make their own runs at your landing craft.

But now we have the problem of getting to England. Germany's historical barge plan doesn't cut it. Even if the RN decides they want to stop the invasion the funniest way, to swamp all the barges by sailing pretty much any vessel in the Home Fleet nearish to them, they literally cannot supply any number troops they land. So to get to England with any ability to fight, they need to develop and construct landing craft for infantry and armour, mobile ports they can use until they can secure actual ports post invasion and an entire merchant marine to supply their armies once they land. This is the bare minimum, and only works if they create magic torpedo bombers that can't possibly fail to stop the Entire Home fleet from having an effect on the landing. If they can't do that (they can't) then they need to start building enough destroyers, cruisers and battleships to counter the Home Fleets inevitable attack on their landing attempt.

That's literally millions of tons of steel, millions of man hours in development and construction for what? Historically the German army was virtually unmotorised, had effectively no artillery corps, no naval support and no support from strategic bombing of any type. Given what they had to build to get there, what are you taking away from the army that's landing on the coast of an industrialised nation that has had literally years to prepare?

[Alkaloid]

On the late 1700s front, it's interesting that a lot of these dates proposed are just after the Jacobite cause collapsed and Britain really started to look more like a single nation on an island than it had previously.