When the Wall Street stock market collapses in October 1929 the developed world is plunged into the Great Depression. In the United States manufacturing output falls by half and one third of workers lose their jobs. The world is just emerging from the slump when the Second World War breaks out. The US enters the war in 1941 when the Japanese bomb Pearl Harbour in Hawaii.
Born on 30 January 1882 at Hyde Park, New York, US, into a wealthy and privileged family. Roosevelt is educated at home by his mother until he is 14.
1900 - He enters Harvard University, receiving a BA in history in 1903. While at Harvard he becomes engaged to Eleanor Roosevelt, a distant cousin and the niece of President Theodore Roosevelt. The couple marry on 17 March 1905 and have six children. Eleanor will have a profound effect on her husband's attitude to social reform.
Following his graduation from Harvard, Roosevelt attends Columbia University Law School. He passes the bar examination in 1907, practising law with a prominent New York city law firm for the next three years. However, he appears indifferent to the legal profession.
1910 - Roosevelt enters politics, winning a seat in the New York State Senate for the Democrats. He is not yet 29. He quickly comes to prominence when as leader of a small faction he forces the party to switch a candidate for the federal Senate.
1911 - He supports progressive New Jersey governor Woodrow Wilson for the Democratic presidential nomination of 1912. Wilson wins the presidency. Roosevelt, who has a longstanding interest in seafaring, is appointed assistant secretary of the navy in March 1913. He resigns his state Senate seat and moves to Washington, DC.
1917 - The US enters the First World War. Roosevelt builds a solid reputation for his administration of the navy.
1920 - He wins the Democratic nomination for vice president, running with presidential nominee James M. Cox, but the Democrats lose the elections to the Republicans. Roosevelt returns to private life.
1921 - He contracts poliomyelitis (polio) while on vacation at Campobello Island, New Brunswick, Canada, in August. For a time he is almost completely paralysed. He will never fully regain the use of his legs and will spend most the remainder of his waking life in a wheelchair. While he recovers Eleanor becomes his public voice.
Roosevelt regains some strength in his legs by swimming in mineralised pools at Warm Springs, Georgia. Warm Springs will become a second home to Roosevelt. He founds a hospital for polio patients there in 1927 and builds a cottage, 'The Little White House', in 1932.
1924 - Roosevelt returns to public life, appearing at the Democratic convention to nominate Alfred E. Smith, governor of New York State, as the party's presidential candidate. He conceals his paralysis, feigning mobility with the use of assistants and walking sticks, and is rarely photographed in his wheelchair.
1928 - He again nominates Smith for president. Smith, in turn, convinces Roosevelt to run to replace him as governor of New York State. Roosevelt wins the governorship but Smith loses the presidency. As governor Roosevelt introduces various social reforms, including tax relief for farmers and public development of electric power. He is reelected governor in 1930 with the biggest majority on record.
1929 - The 'Great Depression' begins with the collapse of prices on the New York stock exchange in October, ushering in a 10-year economic slump in North America, Europe and other industrialised regions. Banks close, manufacturing output falls and unemployment rises dramatically.
By 1932 US manufacturing output has fallen to 54% of its 1929 level and unemployment has risen to between 12 and 15 million workers, or 25-30% of the workforce. As governor of New York, Roosevelt responds by introducing state government welfare, establishing the temporary emergency relief administration to provided unemployment assistance to New York's poor.
1932 - Roosevelt's record in New York makes him a frontrunner for the Democratic presidential nomination. He announces his candidacy in January, wins the nomination in July then embarks on a whirlwind campaign, travelling 12,000 miles during September and October.
Roosevelt pledges "a New Deal for the American people", promising aid to farmers, public development of electric power, a balanced budget and government controls on private enterprise. He wins the November presidential election in a landslide to the Democrats.
Roosevelt quickly launches 'The Hundred Days', the first phase of the 'New Deal'. All banks are closed until legislation allowing those in sound condition to reopen is passed on 9 March. Five hundred million dollars is appropriated for relief grants. Funding is approved for the Civilian Conservation Corps, the Home Owners Loan Corporation and the Public Works Administration. The Agricultural Adjustment Act (AAA) and the National Industrial Recovery Act (NIRA) are passed.
The AAA provides for subsidies to producers of basic agricultural commodities in return for reduced production. It aims to increase prices and thus raise the income of farmers. When the AAA is declared unconstitutional by the Supreme Court in 1936, Roosevelt shifts its focus to soil conservation.
The NIRA establishes a public works program and a body to establish and administer industry-wide codes to control labour conditions, prices and production. However, the body administering the codes is declared unconstitutional by the Supreme Court in May 1935.
The Tennessee Valley Authority is created in 1933. The authority builds dams and hydroelectric power plants in the Tennessee River basin, providing cheap electricity and employment.
Other reforms include welfare payments to the poor, employment programs, government controls on stock trading and bank investments, and protection for depositors' accounts.
Roosevelt is named as 'Time' magazine's person of the year for 1932. "Roosevelt's climb to the presidency represented a physical triumph of the first order," the magazine says. "For a decade he had fought a dogged fight to regain control over his paralysed legs. Today the president-elect can walk in his braces, without crutch, stick, or assisting arm, about 15 steps. Declares his wife: 'If the paralysis couldn't kill him, I guess the presidency won't.' The man of the year's attitude toward his affliction is one of gallant unconcern. After his November election he went to Warm Springs where he addressed others there taking the cure: 'We've shown that we people here have determined to get over the small physical handicaps which after all don't amount to a hill of beans.'"
1934 - In January Roosevelt concludes a treaty with Cuba that cancels a previous arrangement giving the US the right to intervene in Cuban politics but allows the US to retain control of the Guantanamo Bay naval base in Cuba's south.
In another foreign policy move, Roosevelt recognises the Soviet Union. At the same time he starts to rebuild the US fleet, partially in response to increasing militarism in Japan.
At congressional elections held on 6 November the Democrats win by a landslide, taking about 56% of the vote. The result is seen as a vote of confidence in Roosevelt's leadership.
Roosevelt is again named 'Time' magazine's person of the year. "To mankind who always love a doer of great deeds, Franklin Roosevelt showed himself in the figure of a Hercules striving to perform immense but modern labours, of a hero who in the US tradition does all his labours on a neighbourly basis," the magazine says.
"He himself expressed as nearly as it is likely to be expressed, the result of this attitude, the reason for the vote of Nov. 6 when he declared: 'The people of this nation understand what we are trying to do...'"
1935 - Roosevelt introduces the 'Second New Deal'. The Social Security Act establishes a "safety net" of welfare benefits for all Americans. The unemployed are provided with useful public work. Labour's right to bargain collectively is reestablished. Taxes on the wealthy and large corporations are raised.
1936 - Roosevelt wins a second term as president, again with an overwhelming majority. With the economy improving he winds back the New Deal.
1937 - Towards the end of the year the US economy falters and threatens to take the rest of the world along with it. The period comes to be known at 'Roosevelt's Depression'.
In Asia, meanwhile, war breaks out between China and Japan on 7 July.
1938 - On 29 September Britain, France, Germany and Italy sign the 'Munich Agreement' ceding the Sudetenland, the German-speaking area in the north of Czechoslovakia, to Germany in return for an assurance of no further territorial expansion.
In November Roosevelt orders an increase in the production of combat aircraft.
1939 - When the Second World War begins in September Roosevelt convinces the government to introduce military conscription, intensify defence preparations, and support Britain with "all aid short of war." After Germany invades the Soviet Union in June 1941 aid goes to the Russians as well.
1940 - In May the Council of National Defence is established in preparation for the possible entry of the US into the war. At the same time, the production of arms is increased significantly.
Japan joins the Axis alliance with Germany and Italy in September, signing the 'Tripartite Pact', an agreement to carve up the world following victory in the Second World War.
The US responds by placing a ban on the export of steel, scrap metal and aviation fuel to Japan.
In November Roosevelt is reelected for an unprecedented third term as president. He continues the support for Britain, allowing noncash payments for military and other aid and providing US Navy escorts for shipments to the British Isles.
Under the 'Lend-Lease' program introduced in March 1941 Roosevelt agrees to lend navy destroyers to Britain in exchange for the right to lease British territory in the Atlantic for US air and naval bases.
1941 - In April the US takes Greenland under its protection. After Germany invades the Soviet Union on 22 June the Lend Lease is program is extended to the Soviets and US troops are stationed in Greenland.
When Japan occupies southern Indochina on 23 July the US and Britain freeze Japanese assets, an action that has the potential to cripple the Japanese armed forces.
On 14 August Roosevelt and British Prime Minister Winston Churchill issue the 'Atlantic Charter', a joint statement setting out eight "common principles ... for a better future for the world." Drawn up at sea, off the coast of Newfoundland, the charter includes commitments to national sovereignty, democratic government, free trade, improved labour, economic and social standards, freedom of movement, world peace, and the abandonment of the use of force.
In September Roosevelt announces that the US Navy has been ordered to destroy any German or Italian submarines entering US waters and threatening the country's defence. Japan, meanwhile, is asked to withdraw from China and Indochina. Japan refuses but sends envoys to the US for peace talks.
The Japanese air force bombs the US naval base at Pearl Harbour in Hawaii on 7 December, killing 2,403 and wounding 1,178. The US declares war on Japan the following day. Germany and Italy declare war on the US on 11 December. The US responds by declaring war on the two countries.
The Japanese follow-up the bombing of Pearl Harbour with swift invasions of Southeast Asian countries and Pacific islands. By May 1942 they control Hong Kong, Kiribati, Guam and Wake Island, Burma, Malaya, Singapore, Borneo, Indonesia, the Philippines and the north of New Guinea.
Roosevelt becomes commander-in-chief of the US armed forces. The mobilisation for the war effort results in a full economic recovery. There are now more jobs than workers.
Roosevelt embraces Churchill's plan for a "grand alliance" between the Allied forces. The two leaders agree that their primary aim should be the defeat of Germany and that countering Japan should be a US responsibility.
For the third time, Roosevelt is named 'Time' magazine's person of the year. "In his own right and on his own record President Roosevelt stood out as a figure of the year and of the age," the magazine says.
"His smiling courage in the face of panic, his resourcefulness in meeting unprecedented threats to the nation's economy and morale, his sanguine will place him there. The intensity of his feeling for what America can be and therefore will be - a feeling that awakened the country to master its creeping paralysis - these qualities prepared the nation for its struggle in the depth of depression. On a far greater scale, for a far greater cause, against a worldwide sense of hopelessness, those same qualities were called into play when the Japanese on a sunny December morning descended from the sky on Pearl Harbour."
1942 - In 'The Declaration of the United Nations' of 1 January the Allies agree not to make a separate peace with the enemy and pledge themselves to the formation of a peacekeeping organisation (now the United Nations - UN) on victory. Looking beyond the war, Roosevelt attempts to gain the confidence of Soviet leader Joseph Stalin, believing that the maintenance of peace will depend on friendly relations with the Soviet Union.
The military turning point of the war in Europe comes when the German Sixth Army is defeated at Stalingrad (now Volgograd) in the winter of 1942-43. By the end of 1943, the Soviets have broken through the German siege of Leningrad (now Saint Petersburg) and recaptured much of the Ukrainian Republic.
The German offensive in North Africa is stopped at the beginning of November, leaving the Allies free to land in Sicily and Italy.
To the west, the US and British navies gain control of the Atlantic shipping lanes, clearing the way for the 'D-Day' landings on the Normandy beaches in France on 6 June 1944 and the invasion of Germany six months later. Soviet troops, meanwhile, advance from the east.
Half the world away, the Japanese advance suffers its first setback on 7-8 May 1942 at the Battle of the Coral Sea. On 4-5 June 1942 the Japanese fleet is forced to withdraw at the Battle of Midway or risk destruction. By February 1943 the Japanese have been driven out of Guadalcanal at the southern end of the Solomon Islands.
1943 - Roosevelt and Churchill hold the Casablanca Conference on 14 January, declaring that they will except nothing short of unconditional surrender from any of the Axis powers.
From 28 November to 1 December Roosevelt meets with Churchill and Stalin in Tehran, the capital of Iran. The three leaders discuss the details of their joint campaign against Hitler and reaffirm their joint policy of accepting nothing less than an unconditional surrender from Germany.
By the end of the year, the Soviets have broken through the German siege of Leningrad (now Saint Petersburg) and recaptured much of the Ukrainian Republic. By the end of 1944, the front has moved into Eastern Europe.
1944 - On 22 January Roosevelt sets up the War Refugee Board. The board's role is to assist with the rescue of Jews and other ethnic groups threatened by Nazi persecution.
The Battle of the Philippine Sea on 19-20 June 1944 confirms US naval superiority in the Pacific and seals Japan's fate. The capture of Saipan in July puts the Japanese mainland within range of American B-29 bombers.
Beginning in February 1945 extensive firebombing raids will be conducted over Japan, concentrating on the capital Tokyo and the cities of Nagoya, Osaka and Kobe. The raids result in the deaths of tens of thousands of civilians. The most devastating raid occurs over Tokyo on the night of 9-10 March. About 100,000 people are killed, around one million are left homeless and almost half the city is burnt to the ground.
Meanwhile, Roosevelt wins a fourth term as president, again with a reduced but still substantial majority. However, he is suffering from serious heart and circulatory problems and his health is failing.
Putting aside his health concerns, Roosevelt continues to plan for the future of the US and the world once the war is over. His central goal is the formation of an organisation of United Nations.
From August to October representatives of Britain, China, the Soviet Union, the US meet at Dumbarton Oaks, Washington, to develop proposals for the new international body.
1945 - From February 4-11, Roosevelt again meets with Churchill and Stalin. The conference, held near Yalta in the Crimea, concludes with the issuing of the 'Yalta Declaration' committing the Allies to the destruction of German militarism and Nazism.
A conquered Germany will be divided into three zones of military occupation. Soviet forces will remain in Eastern Europe until free elections are held and the people are allowed to choose the form of government under which they will live.
The declaration also announces that a "conference of United Nations" will be held in San Francisco in April.
During the conference, Roosevelt also convinces Stalin to commit Soviet forces to the war against Japan.
Roosevelt travels to his cottage in Warm Springs at the end of March to rest. On 12 April, while sitting for a portrait, he suffers a massive cerebral haemorrhage. He dies a few hours later. The same day Vice President Harry S. Truman is sworn in as president.
Roosevelt's body is carried by train from Warm Springs to Washington for a memorial ceremony. Two million mourners line the tracks. He is buried in the rose garden at Hyde Park.
Both Churchill and Stalin are stunned by Roosevelt's death. "I feel so deeply for you all," Churchill writes to Eleanor Roosevelt. "As for me, I have lost a dear and cherished friendship which was forged in the fire of war. I trust you may find consolation in the glory of his name and the magnitude of his work."
On 7 May, less than one month after Roosevelt's death, Germany surrenders unconditionally. Three months after that, on 15 August, Japan also surrenders.
Stalin fails to honour the Yalta Declaration and does not allow free and fair elections in the Eastern European countries the Soviets occupy after the war. An 'Iron Curtain' falls across Europe and a 'Cold War' develops between the USSR and the West.
A conference to draw up the United Nations Charter is held in San Francisco in the middle of 1945. The Charter is signed on 26 June 1945 by the representatives of the 50 countries attending the conference.
The United Nations officially comes into existence on 24 October 1945, when the charter is ratified by the majority of its 50 signatories.
Roosevelt's solution to the social devastation of the Great Depression offers an interesting counterpoint to that adopted in Europe in general and Germany in particular. Roosevelt's brand of democratic socialism was tolerant and supporting. The national socialism of Germany's Nazi Party was rigid and expansionist. Both solutions were inadequate and the economies of both countries were in the end only completely restored by the outbreak of war. But it was national socialism that started the conflict and democratic socialism that helped to end it.