Russia's natural Iron Curtain--its freezing winters--helped defeat three invading armies which sought to capture Moscow. First came Charles XII of Sweden whose invasion was stopped at Pultava in 1709 when his army, cut off from reinforcements, was weakened further by the weather. In 1812, Napoleon had numbers, initiative, and surprise on his side and managed briefly to capture Moscow, but nepotism (his brother Jerome, no soldier, headed the southern forces which moved too slowly) contributed to delays which stranded Napoleon's weakened army in Russia in mid-winter and forced a hurried retreat. In 1941, the Wehrmacht began an invasion which Hitler directed somewhat erratically and which ended four years later with the occupation of Berlin, but before that Hitler had medals struck which most soldiers called the Order of the Frozen Flesh. Cooper naturally cites other factor besides the weather, and all too frequently he quotes secondary sources at length. It's a competent condensation of three military defeats, but it's all bleak summary and the prose is heavy. The book's total effect is the equivalent of the Russian winter--it will route readers or numb them.