Franklin D. Roosevelt in the context of "First hundred days (United States)"

A declaration of war is a formal act by which one state announces existing or impending war activity against another. The declaration is a performative speech act (or the public signing of a document) by an authorized party of a national government, in order to create a state of war between two or more states.

The legality of who is competent to declare war varies between nations and forms of government. In many nations, that power is given to the head of state or sovereign. In other cases, something short of a full declaration of war, such as a letter of marque or a covert operation, may authorise war-like acts by privateers or mercenaries. The official international protocol for declaring war was defined in the Hague Convention (III) of 1907 on the Opening of Hostilities.

The president of the United States (POTUS) is the head of state and head of government of the United States. The president directs the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces.

The power of the presidency has grown since the first president, George Washington, took office in 1789. While presidential power has ebbed and flowed over time, the presidency has played an increasing role in American political life since the beginning of the 20th century, carrying over into the 21st century with some expansions during the presidencies of Franklin D. Roosevelt and George W. Bush. In the 21st century, the president is one of the world's most powerful political figures and the leader of the world's only remaining superpower. As the leader of the nation with the largest economy by nominal GDP, the president possesses significant domestic and international hard and soft power. For much of the 20th century, especially during the Cold War, the U.S. president was often called "the leader of the free world".

Diplomacy is the communication by representatives of state, intergovernmental, or non-governmental institutions intended to influence events in the international system.

Diplomacy is the main instrument of foreign policy which represents the broader goals and strategies that guide a state's interactions with the rest of the world. International treaties, agreements, alliances, and other manifestations of international relations are usually the result of diplomatic negotiations and processes. Diplomats may also help shape a state by advising government officials.

The Montevideo Convention on the Rights and Duties of States is a treaty signed at Montevideo, Uruguay, on December 26, 1933, during the Seventh International Conference of American States. At the conference, United States President Franklin D. Roosevelt and Secretary of State Cordell Hull declared the Good Neighbor Policy, which opposed U.S. armed intervention in inter-American affairs. The convention was signed by 19 states. The acceptance of Brazil, Peru and the United States as signatories was subject to minor reservations.

The convention became operative on December 26, 1934. It was registered in the League of Nations Treaty Series on January 8, 1936.

Presidential elections were held in the United States on November 2, 1920. The Republican ticket of senator Warren G. Harding of Ohio and governor Calvin Coolidge of Massachusetts defeated the Democratic ticket of governor James M. Cox of Ohio and assistant secretary Franklin D. Roosevelt of New York. It was the first election held after the end of the First World War, and the first election after the ratification of the Nineteenth Amendment gave nationwide suffrage to women.

Incumbent president Woodrow Wilson, a Democrat who had served since 1913, privately hoped for a third term despite severe physical and mental disabilities from a stroke, but he had very little support. Former president Theodore Roosevelt had been the frontrunner for the Republican nomination, but he died in 1919 without leaving an obvious heir to his progressive legacy. The major parties turned to little-known dark horse candidates from the state of Ohio, a populous swing state with many electoral votes. Cox won on the 44th ballot at the 1920 Democratic National Convention, defeating William Gibbs McAdoo (Wilson's son-in-law), A. Mitchell Palmer, and several other candidates. Harding emerged as a compromise candidate between the conservative and progressive wings of the Republican party, and he clinched his nomination on the tenth ballot at the 1920 Republican National Convention.

The Great Depression was a severe global economic downturn from 1929 to 1939. The period was characterized by high rates of unemployment and poverty, drastic reductions in industrial production and international trade, and widespread bank and business failures around the world. The economic contagion began in 1929 in the United States, the largest economy in the world, with the devastating Wall Street crash of 1929 often considered the beginning of the Depression. Among the countries with the most unemployed were the U.S., the United Kingdom, and Germany.

The Depression was preceded by a period of industrial growth and social development known as the "Roaring Twenties". Much of the profit generated by the boom was invested in speculation, such as on the stock market, contributing to growing wealth inequality. Banks were subject to minimal regulation, resulting in loose lending and widespread debt. By 1929, declining spending had led to reductions in manufacturing output and rising unemployment. Share values continued to rise until the October 1929 crash, after which the slide continued until July 1932, accompanied by a loss of confidence in the financial system. By 1933, the U.S. unemployment rate had risen to 25%, about one-third of farmers had lost their land, and 9,000 of its 25,000 banks had gone out of business. President Herbert Hoover was unwilling to intervene heavily in the economy, and in 1930 he signed the Smoot–Hawley Tariff Act, which worsened the Depression. In the 1932 presidential election, Hoover was defeated by Franklin D. Roosevelt, who from 1933 pursued a set of expansive New Deal programs in order to provide relief and create jobs. In Germany, which depended heavily on U.S. loans, the crisis caused unemployment to rise to nearly 30% and fueled political extremism, paving the way for Adolf Hitler's Nazi Party to rise to power in 1933.