By William Manchester and Paul Reid, Little Brown and Co., New York, N.Y. 1182 pages, $40

In the first two volumes of William Manchester’s biography of Winston Churchill, which covered the first 65 years of Churchill’s life, he told the story of a man who was incapable of discouragement. Personal and professional setbacks always seemed to be beckoning. But Churchill possessed the fortitude to overcome, never seeming to doubt himself. In this third and final volume, Manchester, with the assistance of Paul Reid, continues the theme of indomitability as he recounts Churchill’s epochal premiership during World War II and his post-war years as Conservative Party chief and elder statesman.

The third volume has had a lengthy gestation. The second volume, published in 1988, covered Churchill’s “wilderness years” during the 1930′s when, banished from the Tory leadership, he urged without success British rearmament in response to the rising Nazi menace. While working on the third volume, Manchester was felled by two strokes. In 2003, he asked Reid to finish it. What has emerged is a book that is satisfyingly Manchesterian in depth and quality.

As the third volume opens, Churchill has just ascended to the premiership on May 10, 1940 in the wake of Britain’s dissatisfaction with Neville Chamberlain’s leadership during the early months of the war. The Wehrmacht has conquered Poland and is poised to invade the Low Countries and France. In setting the stage for the coming catastrophe, the book explains well the uneasy mood of the times, the Allies’ military unpreparedness, and the fear of what the future portended.

As recounted by the authors, Churchill’s first month in office was disastrous. By early June 1940, the Nazis had conquered France and forced the British Expeditionary Force to retreat from the European continent. Having conquered its neighbors, the Nazis next sought to neutralize Britain, which now stood alone, virtually defenseless. Hitler, who already had his sights set on attacking the Soviet Union, desired a quick pacification of or armistice with the British.

Churchill would have neither. He believed that courage is the finest of qualities because it is the one that guarantees all others. With his forces in tatters, he chose to stand his ground. Rather than compromise with Hitler, Churchill vowed to destroy him. He warned Britons of the dangers ahead. Churchill told colleagues that if the resistance failed, he expected to be dead within three months.

What followed, of course, was the relentless Luftwaffe bombing of English cities and merchant ships. As described by the authors, the bombings of London and Coventry were especially devastating, leaving thousands dead, injured, and homeless. But Churchill remained defiant, all the while preparing to repulse Nazi invaders at the beachhead. During the height of the blitz, he even daringly goaded Hitler by broadcasting: “We are waiting for the long presumed invasion. So are the fishes.”

Churchill possessed a great wit, and the authors enliven their narrative with his best anecdotes. During the London blitz, the Archbishop of Canterbury voiced alarm about Nazi bombs possibly damaging Lambeth Palace. Churchill assured him that everything was being done to protect it. The archbishop then asked what would happen if a bomb scored a direct hit. Churchill replied, “In that case, my dear Archbishop, you will have to regard it as a divine summons.”

As Nazi bombs rained, Churchill asked President Franklin Roosevelt for assistance. As deftly explained by the authors, FDR resisted because 1940 was an election year and American public opinion was dead set against entangling the United States in the war. But Churchill’s relentless cajoling secured food, oil and munitions from FDR. After FDR was reelected, the two leaders then implemented a new method of supplying Britain with military supplies without monetary payment, known as Lend-Lease. Following the 1940 election, FDR convinced Congress to approve it.

America eventually entered the war in December 1941. Churchill now had the ally he needed to defeat the Axis. As explained in detail by the authors, the alliance was constantly fraught with infighting, jealousy, hubris and limited resources. Churchill lamented that the only thing worse than fighting a war with allies was fighting one without them.

Churchill and FDR held 12 strategic conferences during the war. The book recounts each in detail, and does an admirable job of explaining the context, issues and personalities that affected each one. As the war progressed, FDR’s influence increased while Churchill’s waned, a fact of which Churchill was keenly aware. Churchill especially resented the way FDR sought American advantage over post-war British economic activity, particularly in Mideast oil.

By the end of the war, Britain was an exhausted country with massive debts and a falling standard of living. According to the authors, following V-E Day, the British electoral landscape changed quickly. The population wanted overdue reforms in education, housing, healthcare and pensions. During the general election of July 1945, the voters became convinced that Tories could not deliver reform and gave a majority to the Labour Party, thus ending Churchill’s premiership.

At 70, Churchill was considered finished in politics. As explained by the authors, however, Churchill maintained his seat in the House of Commons and held on to the Tory leadership until his April 1955 retirement. He returned to the premiership in October 1951 for a final stint of three and one-half years, helping to maintain the peace in Europe.

For lawyers, the book illustrates the importance of two professional traits, reputation and discretion. Had Chamberlain remained prime minister, Hitler may have invaded Britain. But Hitler did not invade, in material part because of Churchill’s reputation for steadfastness. No less important was Churchill’s maturity in dealing with FDR, who often needlessly enraged him. In the heat of the moment, Churchill vented his anger many times in lengthy cables to FDR. But the cables remained in draft, never to be sent. In holding his fire, Churchill swallowed his pride, but in so doing saved the alliance.

Jeffrey Winn is a partner at Sedgwick LLP.