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Aviation History
1945
1945 - 2009.PDF
FLIGHT OciOBER IITH, I945 Escape Them Never Work of Z S M : Checking Every Ship in Every Port : Measuring Speed by Bow Waves LONG before the invasion of Europe, Britain knew themovements of every ocean-going Nazi ship—whether-* naval unit, tanker or merchant vessel. Most of the names, and often even the cargoes, were known. The blockade-runners .between German-held France and the Far East were beaten because the Navies of Britain and America were told when and where the enemy ships would sail. How. was it done? Largely by photographs. By a card- index system so simple that one would never guess the years of patient study behind it, and yet so fool-proof that a person who had never seen a ship in his life could use it. A system, moreover, which, with small alteration, could be switched to mirror the reviving transport of peace- time Europe. In the K.A.F. and the Navy it was called ZSM. " Z " for the section of the Allied Central Interpretation Unit, which studied the air reconnaissance photographs taken during the war, and " SM " for Shipping Movements. The 6,400-ton German Munsterland, sunk by the big guns of Dover during January, 1944, was one of the vic- tories of ZSM. By means of photographs taken by Coastal The result of an attack on the Jminsterland by a JfoastalCommand Libe^tor in 1943. The Munsterlandresting on the sea-bed off CapGris Nez after being sunk byour coastal guns in January, 1944 Command patrol and reconnaissance aircraft, they watched J her finish a run from the Far East and reach Bordeaux „, in May, 1942. In the Bay of Biscay she was attacked and ' damaged, and had to have an extensive refit. The British experts watched her undergoing repairs at Nantes and in a floating dock near Bordeaux. When, in October, 1934, she moved up the French coast towards the Channel, ZSM passed the word she was in Cherbourg. There Fighter Command aircraft attacked her, and again she had to go into dock for repairs. From Cherbourg, seaworthy again, the Munsterland moved to Dieppe, then to Boulogne. Each move was recorded by the cameras of the R.A.F., and on the card- index at ZSM a few more lines appeared. On the night of January 20th, 1944, the Munsterland tried to run the gauntlet of the Straits of Dover. She was spotted sneaking through the darkness, and from the information of ZSM it was known what the target was. The guns opened up, and the Munsterland was hit and beached. Next day Typhoons gave her the coup de grdce. Recognition Problem At the beginning of the war the R.A.F. had very few „ men capable of identifying shipping from photographs. ^/-^ All the standard reference books gave illustrations show- ing the vessels from the side, not from above. Ironically, it was German shipping books that were the biggest help at first. To-day ZSM has no need for books. Their own records are in themselves the best reference. The reports in those early days were not helpful, some- times the reverse. One day a pilot brought in some photo- graphs of a port area which caused a stir. The officers studying the photographs reported a number of curious dock installations which they had never seen in any enemy port before. They were large and it was felt they might be important. The mystery was not solved until someone realised it was the dock gantries of Southampton which had been photographed by mistake! The interpreters were familiar with German installations, but had never before seen our own from the air. In the summer of 1942 a period of exceptionally fine ather settled over Europe. In the course of a few days *^ lmost every enemy port was photographed by R.A.F. reconnaissance aircraft. It was the chance the interpreters had been waiting for ; they worked now in the sure know- ledge that the tanker they had seen in Kiel, for example, could not possibly be the same one as they had seen at Bordeaux in a photograph the day before. It could not get there in time. So for many weeks they pored over the picture of each , measuring, checking, looking up references, stock-
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