Worst effect of weather in war

Weather has always played an important and unpredictable role in warfare and probably accounts for more losses in a number of campaigns than any other cause and sometimes changes the course of history.   Perhaps the most significant example is the effect of the North Atlantic Oscillation (NAO), which is a result of the see-saw action between the low pressure area that sits over Iceland and the high pressure area over the Azores Islands in the Atlantic.  When the NAO is strong, it drives mild, wet Atlantic winds over Britain and Western Europe, while when it is weak, it allows cold air to come in from Europe, as in the winter of 2007 –2008 in the UK.  This occurred a number of times during WW2, but the worst occasion, in military terms, was in the extremely bad winter of 1941- 42, when the Germans invaded Russia.   The troops were badly equipped for the cold weather, with temperatures dropping to at least –40C, which was bad by even Russian standards.  The effects of the weather were catastrophic for all concerned and greatly influenced the number of deaths during the campaign.  Casualty figures for the German campaign and the Siege of Stalingrad vary, but by the beginning of 1943, for both sides the total casualty figure was probably in the region of over 250,000 troops from the effects of cold weather, disease, starvation, exhaustion and fighting.