The Battle of Britain.

[Dunserving]

21-24 September............................................

Equinox. The time when "spring tides" are at their highest...........

Need I add more?

[RichTO90]

21-24 September............................................

Equinox. The time when "spring tides" are at their highest...........

Need I add more?

Yes, you do, since that is only partially correct. Or, rather, only partially the reason.

Remember, this is not a what if really, although Phylo has yet to actually explain the circumstances that would force 11 Group to withdraw. Thus, all the historical conditions and requirements apply. The Germans required moonlit conditions, just as the Allies did four years later, so the 21st to 24th fits that. But they are not going to be landing at the peak of the tide as some, including myself since I forgot to check my notes, thought. Their plan is to land during the beginning of nautical twilight, which is at roughly 530 AM GMT, but on those days the high varies between 100 AM and 200 AM. So they are landing on the falling tide, some three and a half to four hours later and are facing a growing expanse of that nice wide beach. Holed barges are not necessarily going to ground in shallow water either. Finally, the weather wasn't cooperating from 9 to 20 September, S-Boote operations had essentially been halted during that time because of the sea state, circumstances that make the notion they would launch Sealion somewhat...odd? In fact the weather was so variable that even during the period 21-24 September two of the days failed their criteria since there were either morning fogs along the coast and/or in France and rain squalls. And, no, they are not going to use the fog and rain to "sneak" across, it makes navigation with that large a number of small and inexperienced vessels problematic and, given that it socks in the Luftwaffe they would lose that support as well.

Cheers!

[Dunserving]

...and if they did get ashore on or about 23rd September there's also another problem.

This far north of the equator the sunrise/sunset times are changing at their most rapid rate.
Just a week later there'd have been about 20 minutes less daylight each day in Kent.
A month later 12 hours of daylight would have become 10 hours 13 minutes.
Two months later it's down to 8 hours 30 minutes.
And by Christmas daylight is only 7 hours 40 minutes, with the sun getting no more than 15 degrees above the horizon.

...and for Phylo on Belfast daylight is only 7 hours 15 minutes...
...in Aberdeen daylight drops to 6 hours 40 minutes, and just 12 degrees above the horizon...


Then there's the deteriorating weather, and all that that entails for crossing the channel.........

All in all, landing on a spring tide around the time of the vernal equinox seems to be just a touch preferable!

[RichTO90]

...and if they did get ashore on or about 23rd September there's also another problem.

I'm not so sure but what that may be one of the least of their problems by 23 September... Given that the Luftwaffe has between 9 and 22 September to figure out a way to exceed the "pressure" exerted on 11 Group from 24 August to 8 September so that they will be forced to withdraw from their bases. Of course, without crippling themselves in the process.

BTW, one of the best analysis of RAF and Luftwaffe losses, especially WRT pilot losses, is by my friend Geoffrey Sinclair at http://groups.google.com/group/soc.hist ... of+britain and http://groups.google.com/group/soc.hist ... of+britain&# One of these days I hope to get back to Kew and copy the histories of the pilot training establishment. The fragments that I have are ambiguous WRT how big a problem it was by mid-September. OTOH, we do know that it was a major problem in the Luftwaffe and not just in the Jagdwaffe, the bomber crews were reduced deliberetly about this time so to maintain sortie strength.

Cheers!

[Gooner1]

I'm not sure if Gooner can check the original, but was that missive from Eastern Command dated 3 October or was that when it was filed in the Brocforce War Diary? Furthermore, those conditions do likely apply to the situation as of 10-23 June, when Brocforce was part of Eastern Command.
Cheers!

Ha! That's probably it! I'll check, but as I remember it, the date was when it was signed by the CRA Brocforce.

OTOH, if a 6" howitzer did start banging away at the invasion fleet at maximum range and at 'Normal' rate, by the time the first barge or boat touched land it would have expended at least 120 rounds and probably closer to 200.

And 6" ammunition was produced in comparatively small quantities, only 112,000 between November '39 and April 1940, but at an average of 20,000 per month should still have meant over 200 RPG .. and I can't believe there weren't large stocks from WWI.

As I recall South East Command was only activated in early 1941.

[RichTO90]

As I recall South East Command was only activated in early 1941.

Aaack! You're right, 15 February 1941, I misread?/mistyped? the date going on three years ago. So another fine theory shot to hell.

Cheers!

[RichTO90]

OTOH, if a 6" howitzer did start banging away at the invasion fleet at maximum range and at 'Normal' rate, by the time the first barge or boat touched land it would have expended at least 120 rounds and probably closer to 200.

And 6" ammunition was produced in comparatively small quantities, only 112,000 between November '39 and April 1940, but at an average of 20,000 per month should still have meant over 200 RPG .. and I can't believe there weren't large stocks from WWI.

Yep, and a 25-pdr battery could go through its basic load in about 15-20 minutes of firing if it wanted to. In essence "shortage" of ammunition is a constant that varies relative to the situation. I doubt that the planning called for much more than that the basic load be present with the batteries since the whole British philosophy on ammunition supply was based on pushing forward what was needed as it was called for. In preparing for a major op later in the war they might dump a thousand or even more RPG additional with the batteries, but it would have been unlikely in this situation. That takes us back to the relative capabilities of the Luftwaffe and the RASC drivers of British lorries on British roads.

Cheers!

[LWD]

The impact of intelligence on the likely dates for Sea Lion could then be considerable. If the British had a couple of days warning they could push a fair amount of ammo forward. If they didn't find out until the Ships were on the way I'm not sure how much if any would have reached the guns in time. I have seen estimates that it would take parts of the Sea Lion invasion force as much as 24 hours (or perhpas a bit more) to sail from France to the British coast. If this is the case they will be at sea all of the day before. Would that be enough time to get ammo forward? It would also telegraph the blow to the extent that the RAF could also potentially stage forward if they had been forced out of their forward bases.

[RichTO90]

The impact of intelligence on the likely dates for Sea Lion could then be considerable. If the British had a couple of days warning they could push a fair amount of ammo forward. If they didn't find out until the Ships were on the way I'm not sure how much if any would have reached the guns in time. I have seen estimates that it would take parts of the Sea Lion invasion force as much as 24 hours (or perhpas a bit more) to sail from France to the British coast. If this is the case they will be at sea all of the day before. Would that be enough time to get ammo forward? It would also telegraph the blow to the extent that the RAF could also potentially stage forward if they had been forced out of their forward bases.

Actually the crossing should take something under 12 hours for all elements so the plan was to set off the night before. OTOH that means they will be sailing for practically the entire time exposed to any reaction by the RN. Unless the Luftwaffe has been able to destroy most of the CHL network and the grossly outnumbered German light forces are able to defeat the floating pickets without setting off an alarm (neat trick) it seems unlikely that the RN would not be able to intervene.

Add that the RAF, although not highly capable at sinking the vessels approaching the coast - as Phylo rightly has noted - they were rather good at damaging them in their own ports; something between 10 and 15 percent had been sunk or damaged prior to 21 September.

Remember too that the entire German initial assault wave was expected to take about 72 hours to unload and get ashore. 22 September was "Bright and squally". 23 September was "Showery". 24 September was "Fair with bright periods, showery". So if the Germans elected to launch the evening of 21 September they would have intermittant Luftwaffe support on the first day, but little the second; historically most of the German operations that day were individual reconnaissance and single-aircraft nuisance raids. Likely then in the middle of their initial landings they would be very exposed to retaliation by the RN...and quite able to get ammunition forward with minimal interference.

Fundamentally it looks like a roll of the dice; either the first day succeeds beyond all reasonable expectations or the Germans fail.

Cheers!

[JonS]

FWIW (which probably isn't much) the latest in the HPS Panzer Campaigns series is "Sealion '40"
http://www.hpssims.com/Pages/products/P ... alion.html

Now you can see for yourself

[LWD]

...Actually the crossing should take something under 12 hours for all elements so the plan was to set off the night before. ...

According to one source I looked up the distance from Le Harve to Portsmith is ~100 miles or a bit over 80 nautical miles. I think I've seen estimatates that the top speed of the barges would have been around 6 knots. However isn't their usually a cross current there? That's going to cut into the effective speed as will any wind except one blowing ~ NNE. Wave conditions might also have significant impact on the speed. If you also allow time for forming up after leaving port I'm pretty sure you are over 12 hours. That would also have the barges loading during the day were it would be pretty obvious to any number of observers that something was up.

[RichTO90]

...Actually the crossing should take something under 12 hours for all elements so the plan was to set off the night before. ...

According to one source I looked up the distance from Le Harve to Portsmith is ~100 miles or a bit over 80 nautical miles. I think I've seen estimatates that the top speed of the barges would have been around 6 knots. However isn't their usually a cross current there? That's going to cut into the effective speed as will any wind except one blowing ~ NNE. Wave conditions might also have significant impact on the speed. If you also allow time for forming up after leaving port I'm pretty sure you are over 12 hours. That would also have the barges loading during the day were it would be pretty obvious to any number of observers that something was up.

Somewhere we went over all this three years ago, but I can't find it. Specifically for the landings at Folkestone-Dungeness the initial wave was to come from Calais-Dunkirk, with the main steamer fleet coming from Rotterdam with the second wave. So about 40 nautical miles was the distance for the first wave, given the currents and such 3 knots is probably the best it could maintain...so about 14 hours. The 140 nautical miles from Rotterdam would be by faster elements, probably capable of 10 to 14 knots sustained, so also around 14 hours. The journey from Le Havre to the western beaches is more problematic and would have to start earlier.

BTW, in reviewing the old threads I find that the rough estimate for the size of the five transport convoys crossing the channel was roughly 1 by 13.5 kilometers. Also, that the beaches along the Dungeness-Folkestone coast had already been obstructed by two lines of sea booms.

Cheers!

[Dunserving]

Remember there is a huge tidal flow along the English Channel, first in one direction, then the other. The shape of the coastline forms a narrow pinchpoint in the Dover area. In a slow vessel it is necessary to steer a course well off from directly across. This has the effect of markedly increasing the distance actually travelled - you are working against a current that is trying, and succeeding, in pushing you along the coast.

This link, describing a recent cross-channel swim illustrates the point I am trying to make.

http://www.dailymail.co.uk/news/article ... ssing.html

Despite swimming continuously towards la belle France, this lady actually swam a zig-zag path that totalled 64 miles for a 21 mile crossing.

Of course, if she had made the attempt just after an equinox when the spring tides are higher than usual, and thus the water surges through the Dover Straits even more vigourous......................

[phylo_roadking]

I've missed an interesting two days...

Rich, I thought you meant something more about those two dates that the subsequent discussion revealed - but I don't mean that in a bad way. Both Fleming and latterly Lavery discuss this - Lavery in much more detail; the time of the initial landings was demanded by the Heer...

1/ the nearer to dawn/twilight, the longer the period of daylight they had to establish themselves ashore on the first day;

2/ the nearer to high tide this could be, or to within a band two hours' either side of high tide - longshore currents were greatly reduced - at the exact point of landing, the sea/land terminator the currents aren't offshore, from Folkstone to Dungeness they were tidal rips along the coast. In this narrow band therefore, between those offshore currents and them reaching "dry" land - those landsers struggling ashorre through the tide or trying to handle their rubber dingies would only face a 1knot lateral current....but too far outside of this time slot either side of high tide and this could peak to 8 knots!

The KM of course wanted the maximum period of darkness for THEIR crossing of the Channel, particularly the tonnage massed in Flemish and Dutch ports as it would have the longest to travel....which would IIRC have had the Heer trying to get ashore about 11AM !

The Army won that argument...eventually.

during the period 21-24 September

One thing to remember is that Hitler's eventual order was to have bene a "seven days' readiness" order - that once he gave it, Sealion to begin no later than seven days from that date. The ORIGINAL date for this to be triggered was the 9th IIRC, so it original dates for T-Tag would have ideally been from the 16th on. Only when historically delayed by the three meetings held to consider the state of play, at each of which Hitler refused to give the seven days' readiness order, does T-Tag enter the 21st-24th September timeslot

And, no, they are not going to use the fog and rain to "sneak" across, it makes navigation with that large a number of small and inexperienced vessels problematic and, given that it socks in the Luftwaffe they would lose that support as well.

Remember too that the entire German initial assault wave was expected to take about 72 hours to unload and get ashore. 22 September was "Bright and squally". 23 September was "Showery". 24 September was "Fair with bright periods, showery". So if the Germans elected to launch the evening of 21 September they would have intermittant Luftwaffe support on the first day, but little the second; historically most of the German operations that day were individual reconnaissance and single-aircraft nuisance raids.

I've been trying (without success) to find out details of BoB-period weather for some time....but recently was greatly assisted in this by Patrick Bishop's BoB:Day to Day Chronology....BUT and as well as weather details per day of ops, the suprising thing I found was that very often during August and September the Luftwaffe was prepared to countenance operations in quite "marginal" weather

Yes, historically - in the circumstance of NO Sealion - they didn't fly many sorties during the putative Sealion dates in marginal weather....but looking at Bishop it could very well have been a different case IF Sealion requirements had forced them to.

Actually the crossing should take something under 12 hours for all elements so the plan was to set off the night before. OTOH that means they will be sailing for practically the entire time exposed to any reaction by the RN. Unless the Luftwaffe has been able to destroy most of the CHL network and the grossly outnumbered German light forces are able to defeat the floating pickets without setting off an alarm (neat trick) it seems unlikely that the RN would not be able to intervene.

Lavery - being an RN "small ships" historian - spends a considerable amount of time on this.

The first problem is that they have to trigger a reaction....I.E. be observed by Coastal Command (He puts up a very useful map of Coastal's daily patrol patterns and times over the Channel, Western Approaches and North Sea in mid-1940, something I hadn't found elsewhere) And Coastal's aircraft were seemingly quite restricted in their range at that time...and their observational abilities hampered by bad weather even if they could still fly.

The loss of CHL would be a major problem...but simply missing the approaching Germas would be entirely possible Lavery notes that while RN Liaison offciers were eventually assigned to Army stations - a huge amount of surface contacts simply were never rung through to the nearest RN Command for confirmation of friend or foe status This improved, of course, but the improvement was through the winter and into the fresh "invasion season" of Spring 1941...

The RN DID expend a huge effort on destroyer reconnaissance; Lavery notes (and gives details) on the RN's detroyer patrols during the weeks and months in question; yes, although some three dozen destroyers were "assigned" to various commands for anti-invasion work...in the meantime they were escorting convoys in the Western Approaches (to await recall and a fast dash) ditto convoys through the Channel, in the Thames Estuary etc., etc. He notes there was not a single night went by without a destroyer patrolling from each of the three anti-invasion flotillas...a single destoyer, or several on one patrol course; which left considerable marginal for being in the wrong place at the wrong time

The last layer of the RN's "layered" tripwire was of course the yatchs and trawlers of the Auxiliary Patrol; but this was very much inshore of the british minefields, so was a last line of interception and early warning...

The RN's destroyers couldn't of course operate IN the RN minefields, or often along the South-east coast between them and the shore; this was to be the hunting ground of the Aux Patrol and the RN's MLs/MGBs/MTBs....who with their much shallower draught COULD operate in the minefields.

In those preparations therefore there is considerable scope for

1/ the German invasion groups to simply be mised, some or all of them, by the defenders for one of several reasons. It's unlikely of course that they'd ALL be missed, or even mostly missed....BUT -

2/ the last line of detection being so relatively close inshore means that in many combinations of circumstances the RN's most effective response - her destroyers - are only going to get into contact with the Sealion fleet when is already entering or has entered the minefields and is close to the coast...which means they could have simply been attacking the rearmost elements of the First Wave flotillas.

3/ in which case - like the whole issue of

Yep, and a 25-pdr battery could go through its basic load in about 15-20 minutes of firing if it wanted to. In essence "shortage" of ammunition is a constant that varies relative to the situation.

OTOH, if a 6" howitzer did start banging away at the invasion fleet at maximum range and at 'Normal' rate, by the time the first barge or boat touched land it would have expended at least 120 rounds and probably closer to 200.

....there's only a certain amount of damage the RN has the opportunity and time to do!

Rich -

For example you mention Manston...during the height of the attack on the airfields (24 August - 8 September) it was unserviceable on 24, 25, 29, and 30 August, 1 September (night ops only), and 8 September. So 6 of 16 days in which the Luftwaffe was making a maximum effort to suppress it.

1 Sep - Hawkinge, Rochford and Lympne are unserviceable by night

...there was a difference between being "serviceable"....and being "operational"; as previously discussed, for example - Lypmne was "serviceable" in that aircraft could land and take off from there - but from the large mid-August raids until halfway through September it was "Closed" for operations, with only a skeleton ground staff and minimal (VERY) stores. Closed in the sense that 11 Group wasn't using it...couldn't use it...to position aircraft forward to the coast there.

Furthermore, it is unclear how much the Flak was responsibvle for the RAF losses in France,

From Richards -

"The orders were carried out. But a storm of machine gun and small arms fire rose from the German columns, and three of the first eight crews were at once shot down."

"Not unexpectedly it failed to return. In spite of this two Bomber Command Blenheim squadrons (Nos. 21 and 110) attacked enemy troops and communications along this line of advance during the afternoon; most of the aircraft returned safely to their bases, but in No. 21 Squadron eight out of twelve were severely damaged by fire from the ground."

"Against the more southerly thrust only one operation was undertaken on 11th May Eight Battles of Nos. 88 and 218 Squadrons were ordered to deliver a low-level attack on a column in German territory moving up towards the Luxembourg border. Whether they managed to reach their target area is doubtful. The only pilot to return saw three of his companions succumb to ground fire in the Ardennes"

"At a cost of five machines out of five, and four crews killed or captured, No. 12 Squadron had achieved half its allotted task."

Like all good averages - the flak-vs-fighters percentages of the RAF's losses in France are prejudiced by major "single" incidents like the afternoon of 14th May, when of 71 RAF bombers which took off against German forces at Sedan, forty were brought down by fighters...as opposed to the twenty-four brought down by ground fire above in those four incidents of overwhelming ground fire Richards records.

[JonS]

Lypmne

How does one pronounce that?

"Lime"? "Lip-me"?