Fateful Choices, By Ian Kershaw

Speaking in Boston on 30 October 1940, during his campaign for election to an unprecedented third term, President Franklin Delano Roosevelt made a pledge to his audience. "I have said this before," the president stated, "but I shall say it again, and again, and again. Your boys are not going to be sent into any foreign war." A little over a year later, the United States of America was at war with Imperial Japan and Nazi Germany.

This book explores in fascinating detail, contradicting as it goes, many of our most cherished recollections of the response to Nazi fascism and Japanese imperialism. It asks 10 critical questions which, in the view of Ian Kershaw, predestined the world to a global war of such ferocity that over 50 million people died in the climacteric confrontation.

The decisions which he suggests were "fateful" took place in an 18-month period, from early May in 1940 to the end of 1941. They were as follows: (1) Great Britain decides to fight on; (2) Hitler decides to attack the Soviet Union; (3) Japan decides to seize "the golden opportunity"; (4) Mussolini decides to invade Greece; (5) Roosevelt decides to help Britain; (6) Stalin, unbelievably, decides to trust Hitler; (7) Roosevelt decides to wage undeclared war; (8) Japan decides to go to war; (9) Hitler decides to declare war on the US. Finally, (10) Hitler now overtly embarks upon a policy of "genocide" against the Jews.

Each question reveals the enormity of the dialogue, agreement and disagreement that lay behind its eventual decision. In many cases for example, Hitler's decision to invade Russia the pithy answer would be, "How foolish! Remember Napoleon." But his reasons for doing so were measured, thoughtful, unalterable in his mind and, allowing for the immensity of Russia, inexorably led to defeat.

A reading of Hitler's speeches and Mein Kampf would have led one to believe that he would attack and crush Russia before it attacked him, and then turn his attention to the world domination of the "1,000-year Reich". He did not believe the American war machine would be fully prepared to respond to the Axis until 1945. How wrong he was is one of the most riveting stories in the entire book.

Living on these islands that stood apart from Europe, I had always simplistically believed that the resignation of Neville Chamberlain and the election of Winston Churchill in May 1940 confirmed England's decision to fight on alone. Surprisingly, it was not so, and therein lies the fascinating conflation of untold tales unlocked by the scholarship of Kershaw. Churchill was made Prime Minister on 10 May 1940, the day Germany had launched the Blitzkrieg which in two weeks smashed the French army, occupied Holland, violated Belgian neutrality and drove the British Expeditionary Force to the beaches of Dunkirk. It is always assumed that the arrival of Churchill, unpopular as he was, architect of so many things which had gone wrong in the First World War (including Gallipoli) and a relatively poor Chancellor under Baldwin, asserted the British people's determination to fight on alone. It was not so.

After the war, Churchill wrote in his memoirs: "Future generations may deem it noteworthy that the supreme question of whether we should fight on alone never found a place among the War Cabinet agenda. It was taken for granted and as a matter of course by these men of all parties in the State". This, however, is a complete contradiction of the events as they unfolded, as John Lukacs showed in his superb book Five Days in London: May 1940.

After Churchill's appointment, and from 23 to 28 May, there occurred, in the most analytic detail, conversations, discussions and decisions among five men that would chart the course of Britain's heroic stand, and also confirm the unanimity with which all in government, the civil population and the armed forces would have to face the future. They were Clement Attlee, Prime Minister from 1945-51; Arthur Greenwood, deputy leader of the Labour Party; Lord Halifax, Foreign Secretary; Neville Chamberlain, the former Prime Minister; and Churchill.

My image of Churchill is one of pugnacity, indomitability: a throwback to some imperial vision of Britain, a man of action. But the deliberations of those five days, brilliantly outlined in Kershaw's book, indicate that a wide range of alternatives were considered at that desperate hour. On 26 May 1940, Chamberlain's diary read: "The Prime Minister disliked any move towards Musso[lini]. It was incredible that Hitler would consent to any terms that we could accept, though if we'd get out of this jam by giving up Malta and Gibraltar and some African colonies, he would jump at it. But the only safe way was to convince Hitler that he couldn't beat us."

Chamberlain, in my previous estimation, was a weak prime minister and the architect of the ignoble 1938 Munich Agreement which conceded Czechoslovakia, promised "peace in our time", and whetted Hitler's appetite for Poland. But the extraordinary feature of the five-day debate was the strength and logic of Chamberlain's position. It was he who drafted a memorandum, "Suggested Approach to Signor Mussolini", on 26 May and eloquently argued against it.

These memoranda were exchanged against the appalling background of an unfolding disaster in France, with the Germans pounding the beaches at Dunkirk and uncertainty as to whether the BEF could be rescued. Roosevelt attempted an intervention with Mussolini but was peremptorily rebuffed, and Mussolini declined to receive the American ambassador. An intense debate followed as the storm clouds increased over Dunkirk. No one was really aware within the Cabinet or Foreign Office of what was happening, and the general public barely grasped the enormity of the disaster across the Channel. What was at stake, however, was, in its simplicity, the freedom of the Free World.

If the debate had gone in favour of negotiation with the Germans, the first German prerequisite would have been a change of government in London. As Churchill stated, the Germans would insist upon a puppet government led possibly by Sir Oswald Mosley, the British fascist leader, or more probably, David Lloyd George, admired by Hitler, and a great admirer in turn of the German dictator.

Churchill, backed by Chamberlain, indicated that the British Empire would cease to have an independent position, and the German navy would demand the movement of British ships to German ports, as had been done to the German fleet at Scapa Flow after the First World War. A potential armistice would substantially reduce the capacity of America to aid Britain. The isolationism of America, so strong leading up to the Second World War, would have been confirmed.

Therefore the decision of Britain to fight on meant that Hitler was unable to capitalise on his extraordinary victory in France. The autumn skies of 1940 would deny him victory for the Luftwaffe over the Royal Air Force, and the Battle of Britain, as Churchill described it, was critical to restoring British morale. The Royal Navy would patrol the coastline of Britain against invasion and, by June 1941, Hitler's decision to invade Russia had removed, effectively, all threat of an invasion of Britain and probably Ireland.

On reading this chapter, I was struck by a quality which democracies possess and totalitarian states do not the possibility of exploring all likely alternatives. On 28 May 1940, Britain took a decision which involved long years of denial, defeat, destruction, dependence and renaissance, but that position was arrived at not simply by the pugnacity of Churchill, but by civilised debate among five men, among whom Chamberlain much reviled for the Munich debacle played a critical role. Perhaps in time his reputation may be recrudescent.

There are seven central characters in this book: Churchill, Roosevelt, Hitler, Mussolini, Stalin, Tojo and the Emperor Hirohito. Three were killed: Hitler by suicide, Mussolini shot by partisans, and Tojo hanged for war crimes. Among the victors, Churchill was disowned by the electorate in 1945 and had to wait until 1951 to return to power. Roosevelt died in 1945 during an unbelievable fourth term. Stalin, perhaps the bloodiest, died in his own bed in 1953, but stands exposed for the brutal, callous intriguer he was. It fell to Harry Truman to decide to drop the bomb at Hiroshima and Nagasaki, although again the origins of the Manhattan Project, from which the bomb emerged, date to 1941.

Of all the 10 questions, it is clear that the decision of Britain to fight on and of America to support her by "all means short of war" were decisive. The decision to fight allowed America time to mobilise public opinion and to marshal its enormous productive power. Like Gilbert & Sullivan's Duke of Plaza-Toro, Roosevelt skilfully led his regiments "from behind".

He was aided by an extraordinary group of talented men. They were headed by Cordell Hull, Henry L Stimpson, Frank Knox, Henry Morgenthau, Sumner Wells and, on the army and navy side, General George Marshall and Admiral Ernest J King. Behind these stood the mysterious figure of Harry Hopkins, perhaps closest to the President and the ultimate "fixer". It was he who had the finger on the pulse of public opinion that prodded America and its vast arsenal of democracy and productivity into action. The critical moments in 1940 were the "Destroyer deal", which gave the convoy system added cover against the U-boat menace, the granting of bases by the British in the Caribbean to America and, most importantly, the "lend lease" supply which enabled guns, armourment, aircraft and ships to flow in increasing abundance across the Atlantic.

In his famous fireside chat in which he mentioned "lend lease", Roosevelt used the homely imagery of "lending a neighbour a hose, because his house was on fire". The simplicity of this homily won over the American people, raised America to new heights in the world and gave Britain the lifeline without which it would not have survived. It will forever mark Franklin D Roosevelt as perhaps one of the greatest figures of the 20th century.

The book is brilliantly researched, and hugely thought-provoking as we confront this present world, where conflicts appear at once: more regional, yet curiously international. Anyone who wants to make a commentary on today's problems should eavesdrop on history and be warned of its complexity.

The writer is the chief executive of Independent News & Media