phylo_roadking wrote:Paul, an Anti-Invasion sortie would not require resupply in depth or rota'ing of forces - it would only have lasted 48-72 hours at the very most. And the RN at that extremis would not have cared about losses. Or duties elsewhere. An Anti-Invasion sortie would not have been part of a campaign or strategy, but a one-off survival.
As for the damage they would have done.... there IS a parable...CRETE. Look at the damage the RN did to the two Wehrmacht convoys, in EXACTLY the same sort of commandeered and converted vessels as would have tried to cross .
Do you know what happened at Crete? Your description is inconsistant with modern histories. In the Crete operation the 5th German Mountain division was to be transported by small fishing boats/barges from Greece ~ 300km to the Island of Crete in 3 days. Just before they reached the shores of Crete RN squadrons intercepted them, but failed to wipe them out.
In the initial clash a small convoy of 5 merchant ships transporting 600 troops apiece escorted by 3 Italian destroyers, each with ½ dozen 4.7” guns. This was pursued by a flotilla of 4 x RN destroyers each with Radar and 8 x 4.7” guns. When they finally spotted the Convoy on Radar, they closed with and sank the entire Italian/German convoy plus escorts with minimal loss[“The Naval War in the Mediterranean 1940-1943” Jack Greene & Alessandro Massignani; pp162-164].
Clearly this is an example of the risk that merchant convoys would take transporting troops, however it should be noted that in this case the RN had advanced warning the time of the troop convoy sailing and the route they intended to take allowing for the idealize definitive interception attack to be made under the best conditions [At night with Radar against an enemy with no radar and no warning]. Few warships had radar in 1940 and by 1941 the British intelligence situation had turned around with the Ultra decrypts being intercepted, meaning the RN had what they would lack in 1940.
In Crete on the 21st of May 1941 two RN groups would intercept these amphibious groups at Cape Spada and near Retimo on the next day. RN Group C had 5 x Light Cruisers and 3 Destroyers , while Group D had 3 Light Cruisers and 4 Destroyers. These groups would arrange an over night interception of the amphibious fleets heading towards Crete, while 2 RN battleships would patrol the eastern approaches incase any Italian capital ships showed up.
Over night the RN Group C was able to sneak to about 2km range and ambushed the Cape Spada convoy of 20 small ‘Caique’ boats carrying about 2300 German troops and escorted by a single Italian Torpedo Boat. While the lone Italian put up a fight, hitting one of the destroyers, it was sunk along with 10 of the ‘Caique’ boats. Prompt actions by the surviving ‘Caique’ boats, meant only 300 of the 2300 troops were lost. It was in this action that some of the Greek Caique boats were reportedly swamped by passing warships [“Hitler’s Mountain Troops” James Lucas, pp 74] , but as can be seen , it was far from a fool proof method of attacking convoys, since it took a sweep of 7 Destroyers and Cruisers to just sink 10 ‘Caique’ boats and an escort , while the other 10 ‘Caique’ got away.
The next morning RN Group D intercepting a squadron of 30 x ‘Caique’ boats escorted by another Italian Torpedo Boat near the Retimo. This time the Italian Torpedo boat aggressively put down a smoke screen to cover the ‘Caique’ squadron and charged the approaching RN group, that was also under heavy air attack by Luftwaffe bombers. This combined action drove off the British squadron allowing the second convoy of mountain troops to escape with the loss of only one ‘Caique’, but the amphibious Squadron was forced to return to Greece. Later another convoy would arrive with troops at Crete. Overall it should be noted that over the 6 days, only one coordinated attack by the RN was attempted in which a total of RN 8 cruisers and 7 destroyers assaulted a group of up to 50 x ‘Caique’ boats, ½ dozen warships and a dozen troops ships, sinking ¼ of these boats with 10% RN loses and driving off ¾ of the invading Axis ships/boats.
This is an interesting comparison with “Operation Sealowe”, since these German amphibious squadrons planned to deploy about 50-150 x barges and ferries at a time that on paper could only be escorted by a couple of torpedo boats. In practice however they had 433 Auxiliary patrol craft and planned draw for escorted by up to 2 dozen Minesweepers/Vorpostenboote gun boats each armed with 1-2 x 88mm/4” guns, with considerable Luftwaffe fighter and bomber coverage.
If the Crete action is any indication the Germans will be able to fend for themselves. Problem is that each such RN sweep can only be conducted once every few days when the threat is every day. In desperation it could be done every day but with diminishing returns. What’s more with two dozen German barge squadrons on the go at all times, at most ¼ would be in the water during any given RN sweep. Of those ½ dozen invasion groups hit by sweeps in any given day, maybe 3-4 would be driven off while the last couple get through suggesting , overall almost 90% of these groups should get through… an observation that Churchill himself also made.
Worse still if the RN sweeps ignore these squadron escorts and swamp the barges, they risk being bombarded with hundreds of shells per minute, to say nothing of Luftwaffe intervention. At short range such shells will seriously damage any destroyers they hit possibly preventing them from returning for days or weeks. In Crete ½ the RN attacking ships charged the Axis escorts while the rest chased down the barges. The KM would have enough escorts to meet each of these threats to the squadron. In such cases these KM escorts will no doubt suffer badly in such exchanges, but the inability of the attacking RN warships at Crete to ensure the destruction of only a couple of escorts brings into question the success of such RN tactics, especially in the ‘larger picture’. There would just be too many Axis invasion groups and too few RN sweeps doing too little damage to dramatically alter the out come.
While all the above mentioned invasion forces and counter invasion forces clash at sea , air battles would rage overhead along the lines of the historical “Battle of Britain”. The direct impact of airpower on naval action however may not be as significant as some imagine. Early in the war anti shipping air attacks were not very effective at all. During the historic evacuation from Dunkirk, the Luftwaffe threw 300 bombers at the British fleet for about a week.
In that case the 300 bombers [He-111/Ju-88/Ju-87] sunk/damaged 45 warships 66 transport ships and 80-100 smaller boats sunk. Any ship that is heavily damaged would take weeks or months to repair and bring back to service, so in that context of any invasion of the UK , they are out of the battle and would only exist as enhancements to the existing Harbor defenses.
In terms of air attacks, both sides expected the Luftwaffe to maintain air superiority over the immediate channel crossing areas, however port invasions groups around the country may not be protected at all from the air, other than indigenous flak defenses of the escort ships involved.
The RAF had 660 bombers ‘available’ in mid 1940 with some heavier ‘Whitley’ Bombers carrying up to 7000 Lbs loads [compared to 4000lb maximum for the German bombers]. This suggests the RAF should more than double the Luftwaffe kill rates [adjusting relative delivery to about 2.3 times the German delivery rate]. However the RAF bombers were level bombers with at best a CEP of 200-400m compared to the German bombers at Dunkirk many of which were Stuka Dive bombers with a CEP of 30m.
It maybe that the RAF would be no more effective at sinking the German fleet , as the Luftwaffe was at sinking the Dunkirk rescue fleet. Worse still while the RAF did contest the German bomber attacks at Dunkirk, it was little more than 300 sorties a day and about 30-40 fighters at any time. By comparison the Luftwaffe could draw on up to 1300 Me-109s and 1500 Bombers, of which only about ½ could reach over southern England. That means roughly speaking the other half should be available to cover the channel . Thats >600 x Me-109s fly about 1 sortie a day in reserve to counter RAF attacks over the channel. In other words while the Luftwaffe outnumbered the RAF over the sky’s of Dunkirk up to 6:1 , the RAF would at best match the Luftwaffe 1:1 over the English Channel during ‘Sealowe’. In that situation RAF Bomber Command are likely to suffer severe attrition to the Me-109 , which after all where the best interceptors of their day.
If we are extremely generous to the RAF it could translate into them sinking roughly ~ 250 German ships/boats each week [Luftwaffe success based on “Hitler’s Blitzkrieg Campaign”, pp 258]during the amphibious assault phase in the Kent region, that’s about 6% of the invasion force per week. Per day that’s ~36 x warships /merchants / trawlers and smaller patrol boats and towed barges. At that rate of destruction, it would statistically take > 16 weeks of uninterrupted RAF bomber attacks to completely destroy/sink the entire amphibious fleet, and 8 weeks to reach the 50% German imposed cut off point. Mean while, during the same time period, the ~600 Luftwaffe bombers should be able to sink/damage 90 ships/boats per week with the same level of uninterrupted bombing attacks.
So if we intergrate these two experiences we get 250+ 100 German boats/barges/warships lost each week against 90 +12 RN warships. Roughly 3.5 :1 kill ratio. The germans can count on upto 3400 boats barges and warships suggesting 50% level would be reached after 5 weeks of contineous success, however the RN anti invasion fleet can only count on maximum 90 Cruisers and Destroyers backed up by 40 minesweepers and maybe 300-400 armed trawlers ....maybe 450-500 warships . RN could reach the 50% kill rate after 5 weeks , but would cost their entire anti invasion fleet. But that presupposes that German ground troop action doesn't significantly alter the battle calculus, which it should.
Most people who study WWII think German armor was always to fragile and insufficient in number realtive to the needs; and that slightly better use of allied armor would brutalize the panzer divisions at any trim form 1940 on.