The RN would likely be committing more than 80 ships to the Channel in the event of an invasion, even if the majority are minesweepers, armed trawlers and other similar minor warships. The RN will also be committing them over several days. The German Army cannot land and defeat Britain in a single day; therefore, if the RN can sink the effective German escorts in the first battle, they can crush the invasion fleet at their leisure over the next few days. The German Army cannot fight without food, fuel and ammunition, and the RN can easily stop them doing so.
Right, the RN had hundreds of armed trawlers and such that would enter the fray as the battle moved to the beach. But the battle has to get to the beach for that to happen, that is, the invasion has to brush through the 80 x RN warships that attacked previously.
The problem with crushing the invasion "at their leisure" is that if the first wave lands intact it gets harder to crush the invasion on the beach. The British army in 1940 didn't have that many good "attack" divisions, and unit for unit, the Germans were better. If the Germans got ashore, the British might deploy reserves to contain them (a la Anzio), but to throw them back might not be possible. The barges - the weakest part of the invasion - weren't required to run supplies and more men to an established position, they were needed for the first mass of 100,000 to land. The supply after that could be done by other transports, (warships, motor boats, trawlers, tugs, anything that could make 8kt or better). The exception to that idea would be the 2nd wave, which would require a large barge transportation force. If an "Anzio" situation were to evolve, it might come to a point where the British decide to make peace, or that the Germans reverse the direction and start evacuating, or that they just bear down and decide to ride it out into 1941 in a bridgehead. None of these scenarios are good for the British, so turning the invasion back before it lands would be best I think.
The Luftwaffe does better against the RAF over the Channel, yes. But the Luftwaffe would also be overstretched in the event of an invasion; they have to interdict British movements inland, suppress RAF bases, provide CAS to the troops, hit the main British ports (which are spread over a very wide area), sink RN ships at sea (which they were not very good at doing during 1940), escort every one of these missions and provide CAP over the invasion convoys. There were just too many missions for the available aircraft.
If 80 RN warships go after the invasion convoy in daylight, let's assume the LW response is an all-out counterattack with every plane available against the RN forces attacking, at the maximum achievable sortie rate, in order to defeat that attack. Until that was achieved, no "inland interdiction", no "bombing empty ports", no "attacking RAF airfields". Everything into the Channel, all out, as many sorties as possible, or against RN warships trying to reload ammunition in port. What happens?
Ten or more warships lost only adds up when you have some way to exploit those losses; but if you lose your entire fleet as you cause those losses, it becomes irrelevant. The RN could easily absorb losses to Home Fleet if it meant the destruction of the German ability to invade Britain, because then it could free up ships for other duties.
It's not yet a total war. How many warships could the British afford to lose before they decided to make peace instead? The IJN off Guadalcanal found that the number of sinkings and damage was too much to sustain. But, they were over 2,000 miles from home and had the room to stop fighting for Guadalcanal. Can the RN stop fighting in the Channel?
A little context. These high ammunition expenditures could point to any number of things, from a difficulty hitting/sinking the ships in question, through a gunnery officer taking the opportunity to get some practice against real-life targets, to a failure of IJN fire control. Also, while the surface attack on Ganges commenced at 7:10, her captain ordered her abandoned at 7:12. While it might have took an hour for her to sink, she was not exactly in a condition to do something like, say, land troops. Remember, it's still a win for the RN if the Germans turn back.
I'm guessing that under air sea battle conditions in the most atypical air sea battle in modern history, an RN destroyer with let's say 1,000 rounds of main gun ammunition will fire about 250 or more at aircraft, 250 at the convoy escorts that are trying to shoot at them, will keep 200 in reserve that will not be used, (no captain fires off all his ammunition), and the other 300 at 6 targets in groups of about 50 rounds each, sinking, let's say 4 of them and damaging the other 2.
It's interesting that you use the difficulties the Allies had using mainly air interdiction against shipping into Tunisia as evidence that the RN couldn't cut German supply lines in the Channel, when it could just as easily prove that the Luftwaffe would have difficulty preventing the RN operating. That said, while the Axis may have been able to supply Tunisia, they were doing it at a murderous cost; between January and May, they lost 553,099 tons of shipping, and by April, 50% of ships making the passage were lost.
553,099 tons in 5 months is 110,000 tons per month. If the RN in the Channel in 1940 scored at the Tunisia rate - 110,000 tons per month - against a Sealion campaign, would you say that would be enough, nor not nearly enough, to stop the invasion?
The Axis in Tunisia had another big advantage, distance. To interdict them, the Allies had to travel a lot further than they would have had to to in the Channel. This reduces the effectiveness of air interdiction, and made it a lot riskier to deploy surface raiders.
Bone and Malta were about 6 hours steaming from the major Axis ports. How much closer did they need to be?
5,000 rounds is a lot, but it's not that much expended against manoeuvring destroyers at long range. For other battles, we can look at Cape Passero, where Ajax expended 490 rounds and 4 torpedoes to sink two Italian destroyers, cripple a third, and heavily damage a fourth.
Ajax had radar fire control in that battle, hence the big difference in performance.
And remember, the RN can easily rearm and resupply, as it's operating at only a few hours steaming from its bases. Ammunition expenditure is of little consequence compared to the possible goals.
Yes, from the ammunition expenditure profile I sketched up response, I think to win the battle and repulse the invasion, I think it's pretty clear the RN would need to do exactly that, plus use air and RN aux. forces. That it did not have the ammunition aboard the RN 80 warships otherwise to repel Sealion in one go.
Firstly, it's disingenuous to elide the full spectrum of German escorts, from the 10 destroyers down to motorboats with machine guns, into a single category of 'escort'. The Kriegsmarine had very few ships that could effectively engage a British destroyer.
Two things. First, when the captain of Jarvis Bay turned and challenged the Scheer, do you think he was under the illusion he could "effectively engage" a pocket battleship? What do you think he was
doing? Second, if an RN destroyer group encounters a dozen enemy motor boats sailing ahead of the convoy, do you think they might attack them, or just wave and sail on by?
Kurita was operating a considerable distance from any Japanese fighter cover, in an area where the USN had effective air supremacy. The airspace over the Channel would be a lot more contested. We also have an example of the RN operating against landing forces in waters controlled by the Luftwaffe at Crete. Here, despite operating without any fighter cover, and operating far from bases where it could resupply with AA ammo, the RN managed to turn back the entire German landing force. It's not hard to conjecture that they would see similar results in the more favourable scenario of the Channel.
Samar is just an example of an air sea battle where the overwhelming surface superiority didn't pan out due to the grinding effects of constant - even if largely ineffective - air attacks. You list a bunch of reasons why you think this example won't play in an air sea battle in 1940. But we don't really know, do we?
We don't have many indications of this theory actually working, though; the RN was often willing to close targets armed with similar weaponry. It's worth looking at the Battle of the Atlantic here; I can't find a single case where a British escort was damaged by a U-boat's deck gun, while the RN was very willing to close the range on them.
I was picturing it that if an RN destroyer went right in close against 40 ships that these might have more than one submarine deck gun. Am I wrong on that?[/QUOTE]