Logistical Question-Change the date of D-Day

[TFSmith121]

True, and thanks

True, though I think to compare like-with-like we have to use other amphibious operations. Anzio took four months, Gallipoli just plain didn't undergo the transition, and it's hard to come up with other examples from pre-Overlord.

Also, just as a friendly note, if you title your posts and they're part of a sentence then please re-state the sentence in the body. It's easier to follow if you don't have a sentence split between title and body

Yes, I usually try to carry the title sentence over to the first paragraph in the body of the post, but I missed it. Thanks.

On the like-with-like, however, there are some pretty significant differences between the resources/goals of a ROUNDUP/OVERLORD analog (in '43 or '44) and both SHINGLE and Gallipoli.

SHINGLE was - essentially - designed as a flanking move/amphibious envelopment for 5th Army's overland drive; for a variety of reasons, however, it was too far north of the 15th AG's line to really function as such, and it was too weak to provide a separate line of advance - hence the stalemate until spring (launching SHINGLE in winter didn't help, of course).

Gallipoli is different because the assault force, once it went ashore, was essentially still horse-drawn; the differences in tactical and operational maneuver with a motorized force like the 21st AG was night and day.

In a lot of ways, the situation the Allied commanders at Gallipoli - in terms of technique once the landing force was ashore - had more in common with the Chileans at Quintero Bay in 1891 or the Americans at Santiago in 1898.

Best,

 

[Saphroneth]

Okay, fair enough.

One thing I find strange is that there's this perception that OVERLORD was a close run thing. It's probably because Omaha gets all the attention - seeing hundreds of American privates machine gunned down is more photogenic than seeing teams of British/Canadian/American troops efficiently clear the beaches with little fuss - but it's very far from the truth.

 

[Simon]

If they decide to go in 1943 would they be able to make the Mulberry harbours in time? We know now that they weren't vital with large amounts of supplies being able to be landed across the beaches, but they didn't back then. As I understand it because they didn't think the capture of a large enough operating port would be feasible in the initial timeframe the Mulberries gave them the confidence to invade.

 

[TFSmith121]

Yep; the success at UTAH was (somewhat) chancy, but

Okay, fair enough.

One thing I find strange is that there's this perception that OVERLORD was a close run thing. It's probably because Omaha gets all the attention - seeing hundreds of American privates machine gunned down is more photogenic than seeing teams of British/Canadian/American troops efficiently clear the beaches with little fuss - but it's very far from the truth.

The success at UTAH was (somewhat) chancy, but there was also an advantage of having the ADC in the assault wave...

Best,

 

[TFSmith121]

The British had been considering the precursors of

If they decide to go in 1943 would they be able to make the Mulberry harbours in time? We know now that they weren't vital with large amounts of supplies being able to be landed across the beaches, but they didn't back then. As I understand it because they didn't think the capture of a large enough operating port would be feasible in the initial timeframe the Mulberries gave them the confidence to invade.

The British had been considering the precursors of the MULBERRIES for some time (since 1915, in the most general sense) and the GOOSEBERRY idea (blockships to create a sheltered anchorage) were not anything particularly out of the box.

The supply over the beach idea is worth considering some, as well; worth remembering that the US, for example, had been much been considering it since 1920 or so, in terms of amphibious operations, and the Allies had managed it (historically) in the Pacific and Med by the time of OVERLORD.

Best,

 

[Carl Schwamberger]

If they decide to go in 1943 would they be able to make the Mulberry harbours in time? We know now that they weren't vital with large amounts of supplies being able to be landed across the beaches, but they didn't back then. As I understand it because they didn't think the capture of a large enough operating port would be feasible in the initial timeframe the Mulberries gave them the confidence to invade.

The British had been considering the precursors of the MULBERRIES for some time (since 1915, in the most general sense) and the GOOSEBERRY idea (blockships to create a sheltered anchorage) were not anthing particularly out of the box.

The supply over the beach idea is worth considering some, as well; worth remembering that the US, for example, had been much been considering it since 1920 or so, in terms of amphibious operations, and the Allies had managed it (historically) in the Pacific and Med by the time of OVERLORD.

Best,

To amplify Smiths remarks. Over the beach supply was sustained at Gallipoli, nothing new there. Both the Brits and US had examined the solutions for that in 1941-42. The Corps size force on Guadalcanal was sustained across the beach without docks, cranes, rail, or sturdy warehouses. A year later Sicily saw the better part of a army group supplied cross beach for several weeks, until all the port capacity was opened. At Anzio a 'corps' of five heavily reinforced divisions was supplied cross beach from January through June. The tiny fishing ports of Anzio & Nettuno were designed for fishing boats and not larger cargo ships.

When planning for invading NW Europe started in ernest in 1942 it was soon understood from French spies & other sources the German strategy then was to defend the ports & deny them as long as possible to the invaders. Hence Montbattens famous remark from the summer of 1942 that 'we will have to bring our own port. Design of what became the Mulberrys started then.

The core of the Mulberrys, the floating docks, were tested on a Scottish beach in January 1943. Design refinement and stocking of some material went on through 1943, but actual constructing of the bulk of the material for the two Mulberrys, and the third Quiberon Bay prefab harbor, did not start until late 1943. In other words the basic design was tested at the start of 1943, and the equipment for three prefab harbors assembled in five-six months & ready in May 1944.

I dont have numbers at hand for the Brit side, but during July and August cross beach supply through Utah beach ammounted to about 65% of that though the Omaha beach Mulberry, which had lost its docks but still had break waters & the other equipment. Despite of the loss of the docks to the June storm and other sundry problems the US Mulberry, and the cross beach supply at Utah met planned goals. One of the US Army Green Books 'Logistics in Overlord' has a extensive analysis of the US logistics effort and several tables showing the expected and actual throughput of supply in Normandy.

Once the Allies got hold of Cherbourg they put a mass of manpower and technology into it. The nominal peace time intake was between 8,000 & 10,000 tons per day. At the start of September the intake surged to over 24,000 tons per day. That was accomplished by adding a second railroad spur & loading area, upgrading docks with more generators/lights/cranes, installing paved beaching ramps for LST and smaller barges to offload cargo ships, and adding thousands of square meters of roofed storage. For the remainder of the year the intake average around 20,000 tons per day, dropping as the winter weather set in.

 

[TFSmith121]

Nicely summarized...and for what its worth, it's not

To amplify Smiths remarks. Over the beach supply was sustained at Gallipoli, nothing new there. Both the Brits and US had examined the solutions for that in 1941-42. The Corps size force on Guadalcanal was sustained across the beach without docks, cranes, rail, or sturdy warehouses. A year later Sicily saw the better part of a army group supplied cross beach for several weeks, until all the port capacity was opened. At Anzio a 'corps' of five heavily reinforced divisions was supplied cross beach from January through June. The tiny fishing ports of Anzio & Nettuno were designed for fishing boats and not larger cargo ships.

When planning for invading NW Europe started in ernest in 1942 it was soon understood from French spies & other sources the German strategy then was to defend the ports & deny them as long as possible to the invaders. Hence Montbattens famous remark from the summer of 1942 that 'we will have to bring our own port. Design of what became the Mulberrys started then.

The core of the Mulberrys, the floating docks, were tested on a Scottish beach in January 1943. Design refinement and stocking of some material went on through 1943, but actual constructing of the bulk of the material for the two Mulberrys, and the third Quiberon Bay prefab harbor, did not start until late 1943. In other words the basic design was tested at the start of 1943, and the equipment for three prefab harbors assembled in five-six months & ready in May 1944.

I dont have numbers at hand for the Brit side, but during July and August cross beach supply through Utah beach ammounted to about 65% of that though the Omaha beach Mulberry, which had lost its docks but still had break waters & the other equipment. Despite of the loss of the docks to the June storm and other sundry problems the US Mulberry, and the cross beach supply at Utah met planned goals. One of the US Army Green Books 'Logistics in Overlord' has a extensive analysis of the US logistics effort and several tables showing the expected and actual throughput of supply in Normandy.

Once the Allies got hold of Cherbourg they put a mass of manpower and technology into it. The nominal peace time intake was between 8,000 & 10,000 tons per day. At the start of September the intake surged to over 24,000 tons per day. That was accomplished by adding a second railroad spur & loading area, upgrading docks with more generators/lights/cranes, installing paved beaching ramps for LST and smaller barges to offload cargo ships, and adding thousands of square meters of roofed storage. For the remainder of the year the intake average around 20,000 tons per day, dropping as the winter weather set in.

Nicely summarized...and for what its worth, it's not like pontoon bridges, floating bridges, and the like were new technology...

Best,