Sunday, 15 September 2013

Normandy numbers (1)

Pass the ammunition

One of the subjects I continually return to is Normandy. Not just D-Day but the campaign through to the liberation of Paris. It seems to me that the battle for the history of the campaign is as bitter as the actual fighting. If we leave aside the French and Germans (which we really shouldn't), we have an on going three way battle between the Americans, British and Canadians about who did what, how good they were (or not) and how bad Monty was.

My motto is "when the going gets tough the tough get the numbers and do the hard yards". There is a lot of good data about Normandy and our understanding of the campaign will be enhanced (even if the arguments are not resolved) by its full and sensible use.

I have recently been re-reading Max Hastings' book "Overlord" (Pan 1984). Appendix 5 contains "Some British Administrative Statistics" which I assume are from 21 Army Group. The data is familiar to me but I can't pin down the precise source. Probably not the best place to start a crusade for fact based history but certainly it is a first step. If anyone knows where this data originally came from, please let me know.

The data is for the period 12 June 1944 onwards. It gives rounds per month by gun type and rounds per gun per day. I have analysed this data and drawn up some graphs.

This first graph shows the rounds used per month. June numbers are smaller because the data is from 12th only. However, what started my interest is the large amount of mortar ammunition used in June. I assume because the artillery build-up, over the beaches, took time.

To take a closer look at the numbers I analysed the percentage contributions from each gun type. Mortar rounds are nearly 30% of total ammo use in June.

I then developed some "effective fire" values using some very helpful data I found at:
The effective fire values are based on the square root of the weight (in kgs) of the HE content of the shells. This shows, for a given weapon type, the relative effectiveness of its fire. Example values are 0.7 for a 3" mortar, 0.9 for a 25-pdr, 2.3 for a 5.5" gun and 3.6 for a 7.2" gun.

What I find really interesting about this data is the weight of fire contributed throughout the campaign by a fairly small number of medium and heavy guns (~450 guns out of some 2,500 total including mortars) but also the contribution made by divisional 3" and 4.2" mortars.

Time to find some data on American ammunition usage.....