War broke out unexpectedly following the July Crisis in 1914. Austria-Hungary declared war on Serbia, followed quickly by the entry of most European powers into the First World War.

The United States entered the war against the Central Powers in 1917 and President Woodrow Wilson largely shaped the peace terms. His war aim was to detach the war from nationalistic disputes and ambitions.

The Decree on Peace was published in the Izvestiya newspaper, #208, 9 November 1917. It proposed an immediate withdrawal of Russia from World War I.

On 8 January 1918, Wilson issued the Fourteen Points. They outlined a policy of free trade, open agreements, and democracy. While the term was not used, self-determination was assumed.

During the autumn of 1918, the Central Powers began to collapse. Desertion rates within the German army began to increase, and civilian strikes drastically reduced war production. On the Western Front, the Allied forces launched the Hundred Days Offensive and decisively defeated the German western armies.

In late 1918, Allied troops entered Germany and began the occupation.

In late 1918, American, Belgian, British, and French troops entered the Rhineland to enforce the armistice. Before the treaty, the occupation force stood at roughly 740,000 men.

From January 1919 to March 1919, Germany refused to agree to Allied demands that Germany surrender its merchant ships to Allied ports to transport food supplies. Some Germans considered the armistice to be a temporary cessation of the war and knew, if fighting broke out again, their ships would be seized.

In June 1919, the Allies declared that war would resume if the German government did not sign the treaty they had agreed to among themselves. The government headed by Philipp Scheidemann was unable to agree on a common position, and Scheidemann himself resigned rather than agree to sign the treaty.

On 28 June 1919, the fifth anniversary of the assassination of Archduke Franz Ferdinand (the immediate impetus for the war), the peace treaty was signed.

Both Germany and Great Britain were dependent on imports of food and raw materials, most of which had to be shipped across the Atlantic Ocean. The Blockade of Germany (1914–1919) was a naval operation conducted by the Allied Powers to stop the supply of raw materials and foodstuffs reaching the Central Powers.

In March 1921, French and Belgian troops occupied Duisburg, Düsseldorf, and other areas which formed part of the demilitarized Rhineland, according to the Treaty of Versailles.

The commission was required to "give to the German Government a just opportunity to be heard", and to submit its conclusions by 1 May 1921.

On 5 May 1921, the reparation Commission established the London Schedule of Payments and a final reparation sum of 132 billion gold marks to be demanded of all the Central Powers. This was the public assessment of what the Central Powers combined could pay, and was also a compromise between Belgian, British, and French demands and assessments. Furthermore, the Commission recognized that the Central Powers could pay little and that the burden would fall upon Germany.

On 24 January, the American garrison started their withdrawal from the Rhineland, with the final troops leaving in early February.