Austria-Hungary declared war on Serbia on July 28, 1914, marking the official start of World War I.

The Central Powers consisted of Germany, Austria-Hungary, and Italy, while the Allied Powers included France, Russia, and Great Britain.

The Battle of the Somme, fought in 1916, resulted in heavy casualties on both sides and marked a shift in the momentum of the war.

The Treaty of Versailles, signed in 1919, officially ended World War I and imposed harsh conditions on Germany.

Germany invaded Poland on September 1, 1939, marking the start of World War II.

The Axis Powers consisted of Germany, Italy, and Japan, while the Allied Powers included the United States, Great Britain, and the Soviet Union.

The Battle of Stalingrad, fought in 1942-1943, was a major turning point in World War II, resulting in a decisive victory for the Soviet Union.

Little Boy was the atomic bomb dropped on Hiroshima on August 6, 1945, resulting in widespread destruction and loss of life.

Italy was the first Axis power to surrender in World War II, signing an armistice with the Allies in September 1943.

The Yalta Conference, held in February 1945, brought together leaders from the United States, Great Britain, and the Soviet Union to discuss the postwar world order.

The United Nations was established in 1945 to promote international cooperation and prevent future wars.

The Cold War was a period of geopolitical tension between the United States and the Soviet Union from the mid-1940s to the early 1990s.

The Soviet Union launched Sputnik 1, the first artificial satellite, into space in 1957, marking a major milestone in the Space Race.

Fidel Castro led the Cuban Revolution and served as the country's prime minister from 1959 to 1976 and as its president from 1976 to 2008.

The dissolution of the Soviet Union in 1991 marked the end of the Cold War and the collapse of the Eastern Bloc.