The Department of Defense used to be called the Department of War from 1789 to 1949. The name was changed to make the agency more palatable to the American public, which was weary of war after two world wars and a decade-long Great Depression.
World War I (the Great War) began on July 28, 1914 and ended on November 11, 1918. Over nine million combatants were killed. The Armenian Massacre, the twentieth century's first major genocide, began in April 1915 and resulted in the deaths of 1.5 million Armenians. Four major imperial powers (the German, Russian, Austro-Hungarian, and Ottoman empires) ceased to exist. Communism took hold in Russia.
The 1918 influenza pandemic killed between 50 million and 100 million people worldwide and may be a result of trench warfare. The League of Nations was created in 1919 and dissolved in 1946. The U.S. stock market crashed in late October 1929 and ushered in a decade of economic depression that spread globally.
World War II officially began in Europe on September 1, 1939, the U.S. entered the conflict on December 7, 1941 with the Japanese attack on the U.S. naval fleet stationed at Pearl Harbor in Hawaii, and the war ended on September 2, 1945. Over one hundred million people from thirty countries served in military units. Between fifty million and eighty-five million combatants and civilians lost their lives, making WWII the deadliest conflict in world history. Over six million Jews were systematically murdered by the Nazis during the Holocaust.
In 1945, two atomic bombs were dropped on the Japanese cities of Hiroshima (August 6th) and Nagasaki (August 9th). The Third Reich and the Japanese and Italian empires collapsed. The U.S. and the Soviet Union emerged as the world's two superpowers. The United Nations was created on June 26, 1945 with the signing of its charter. The U.S. Marshall Plan was devised in June 1947 to rescue a devastated Europe.
There were just twenty years between the two world wars.
An Iron Curtain swept over Eastern Europe as the Soviet Union spread its influence and communism on war-weary nations. The Cold War period began in 1947 and ended in 1991.
India was partitioned on August 14, 1947 as the new state of Pakistan was declared one day prior to India's independence from British rule. Israel declared its independence on May 14, 1948. China became a communist nation -- The People's Republic of China (PRC) -- on October 1, 1949 once the Nationalist Party forces evacuated to Taiwan.
Earth's first satellite, Sputnik, was launched by the Soviets on October 4, 1957 and ushered in the Space Race between the U.S. and the Soviet Union.
And for those of us who are old enough to remember, President Dwight David Eisenhower, a retired five-star general who became the 34th president of the United States, warned the American public of the Military-Industrial Complex in his farewell address to the nation on January 17, 1961.
President John F. Kennedy was assassinated on November 22, 1963. American participation in the Vietnam War was then escalated. President Johnson declared a War on Poverty on January 8, 1964.
Neil Armstrong was the first man to walk on the moon on July 21, 1969 as part of the Apollo 11 mission.
The Berlin Wall was erected on August 13, 1961 and was a real and symbolic divider of Berlin and Europe until November 9, 1989. Eastern European revolutions began in 1989 that led to self-rule democracies. The Soviet Union was dissolved in 1991. The European Union launched the Euro as its currency on January 1, 1999.
Since the 1950s, the U.S. was a major participant in the Korean War, the Vietnam War, and the Gulf War; regime change in Iran, Iraq, Afghanistan, and other nations; as well as launched a worldwide War on Terror that included the use of drones. 911 was on September 11, 2001 when almost 3,000 people lost their lives on U.S. soil.
In quick response to the September 11th attacks, The US PATRIOT Act of 2001 was signed into law by President George W. Bush on October 26, 2001 after a two-day review and passage in the U.S. Congress. The Patriot Act rolled back many personal freedoms. It was supposed to be a temporary act, but most of its provisions have been made permanent.
The Arab Spring began in Tunisia on December 18, 2010 and spread throughout the Middle East and north Africa. It spread from country to country, removing dictators and inspiring democratic reform through peaceful protest, resistance, armed violence, and civil war.
The Syrian civil war began on March 15, 2011. There are now two million Syrian refugees who fled to neighboring countries, more than four million refugees in Syria itself, over 100,000 deaths in the two-year civil war, including 1,400 deaths in the Damascus suburbs by a chemical weapons attack using sarin gas on August 21, 2013.