The Cold War was the open yet restricted rivalry between the United States and the Soviet Union and their allies that shaped international politics from the end of World War II until 1991. It was fought on political, economic, and propaganda fronts, with only limited recourse to weapons: the Berlin blockade and airlift, the Marshall Plan, NATO and the Warsaw Pact, the nuclear arms race, the Berlin Wall, the Cuban missile crisis, the proxy wars in Korea, Vietnam and Afghanistan, détente and its collapse, and finally the reforms of Mikhail Gorbachev that allowed the Berlin Wall to fall in 1989 and the Soviet Union to dissolve in 1991.
World War I (28 July 1914 – 11 November 1918) began with the July Crisis after the assassination of Archduke Franz Ferdinand at Sarajevo and ended with the Armistice of 11 November 1918. The Central Powers — Germany, Austria-Hungary, the Ottoman Empire and Bulgaria — fought the Allies — France, Great Britain, Russia, Italy, Japan and, from 1917, the United States. Artillery and machine guns forced armies into trenches from the Channel to the Swiss border; gas, tanks and aircraft were used on an industrial scale. In the Middle East the Ottomans fought at Gallipoli, in Mesopotamia and Palestine, and against the Arab Revolt of 1916; the Battle of Megiddo in September 1918 opened the way to Damascus and the armistice at Mudros. American entry in April 1917 gave the Allies decisive weight in 1918, when the Hundred Days offensive broke the Hindenburg Line and forced Germany to seek an armistice. Casualty figures differ by source and definition: Britannica reports some 8,500,000 soldiers dead and around 13,000,000 civilian deaths, the U.S. War Department table of February 1924 totals 8,528,831 soldiers killed and died among 65,038,810 mobilised, and the Imperial War Museums give an estimated 16 million soldiers and civilians dead. The peace settlement — the Treaty of Versailles signed on 28 June 1919, followed by the treaties of Saint-Germain, Neuilly, Trianon and Sèvres, and Lausanne in 1923 — remade Europe and the Middle East, created the League of Nations, and has been debated ever since for the conflicts it helped to set in motion.