of western Europe and normalize relations between Germany and the Allied powers of western Europe. 1926 January 3 Theodoros Pangalos declares himself dictator of Greece. January 31 British and Belgian troops leave Cologne, Germany. April 4 Greek dictator Theodoros Pangalos is elected president. April 24 The Treaty of Berlin is signed by Germany and the Soviet Union, which declares neutrality if either country is attacked within the next five years. September 8 Germany joins the League of Nations. December 25 Emperor Taishō dies, and is succeeded by his son Hirohito as the Emperor of Japan. 1927 April 12 The Shanghai massacre of 300-5,000 communists, perpetrated by the Kuomintang, marks the end of the First United Front and the beginning of the Chinese Civil War. May 20 Saudi Arabia and the United Kingdom sign the Treaty of Jeddah. June 7 Peter Voikov, Soviet ambassador to Warsaw, is assassinated by a White movement activist. November 12 Leon Trotsky is expelled from the Soviet Communist Party, leaving Joseph Stalin with undisputed control of the Soviet Union. December 14 Iraq gains independence from the United Kingdom. 1928 May 3 The Jinan incident begins, a limited armed conflict between the Republic of China and Japan. May 28 Foundation of the Chinese Red Army. June 4 Huanggutun incident: Japanese agents assassinate the Chinese warlord Zhang Zuolin. August 2 Italy and Ethiopia sign the Italo-Ethiopian Treaty, pledging cooperation and friendship. August 27 The Kellogg–Briand Pact is signed in Paris by the major powers of the world. The treaty outlaws aggressive warfare. October 1 The Soviet Union launches the first five-year plan, an economic effort to increase industrialization. November 6 Herbert Hoover wins the 1928 US president election defeating Al Smith. 1929 February 9 Litvinov Protocol is signed in Moscow by the Soviet Union, Poland, Estonia, Romania, and Latvia. The Pact outlaws aggressive warfare along the lines of the Kellog-Briand Pact. February 11 Italy and the Holy See sign the Lateran Treaty, normalizing relations between the Vatican and Italy. March 4 Herbert Hoover is inaugurated as President of the United States March 28 Japan withdraws troops from China, ending the Jinan incident. April 3 Persia signs Litvinov's Pact. June 7 The Lateran Treaty is ratified, making the Vatican City a sovereign state. July 24 The Kellogg–Briand Pact goes into effect. August 31 The Young Plan, which sets the total World War I reparations owed by Germany at US$26,350,000,000