In 1940, as in 1807, only Great Britain remained at war with the conqueror of Europe. After Dunkirk the British awaited the worst, momentarily expecting invasion. Winston Churchill, who had replaced Chamberlain as prime minister in May during the military debacle, rose to the summit of heroic leadership in adversity. To parliament and the British people he promised nothing but ""blood, toil, tears, and sweat."" He pledged implacable war against ""a monstrous tyranny, never surpassed in the dark, lamentable catalogue of human crime."" To the American democracy across the Atlantic he appealed, ""Give us the tools, and we will finish the job."" The United States only reluctantly began to respond. So goes the standard textbook version of perhaps the most momentous year in British history. But there is nothing standard about Laurence Thompson's brilliant study of Britain in 1940. Although it retells the story of Churchill's replacement of Chamberlain, of Dunkirk, Oran, and the Battle of Britain, 1940 is not merely a factual narrative of chronological history; It is a book with a thesis. For this is a book about the paralyzing insanity of war, a work as meaningful to the 1960's as Hardy's treatment of the Napoleonic wars in The Dynasts was to the generation before World War I. With consummate control, the author discusses the events of 1940 and illustrates how weak is man even in glory and how thin is the veneer of civilization. Mr. Thompson reduces such giants as Churchill and Roosevelt to the men that they were, and he does so in polished prose. His gift for turning an incisive phrase is prodigious.