World War I
World War I, also known as The Great War (until World War II), lasted for Europe from 1914 until November 11th, 1918. Entry into the war for the United States wasn't until April 1917. It saw the creation and implementation of some of the most horrific weapons, such as machine guns, chemical weapons, tanks and flamethrowers. The greatest repercussion of the war was World War II. The economic ruin of Germany caused by the terms of their surrender led to the Wiemar Republic's hyperinflation and the rise of Hitler and the Nazi party.
The typical face of the war is the western Europe trench battles, but one must not forget that, due to the mass European colonization in Southeast Asia and Africa, both these areas saw fighting. There was also a theater of the war in the Middle East, as the Ottoman Empire had allied with the Central powers (Germany, Austria-Hungary). The Ottoman Empire was broken up after the war.
Speech Relevance
Reagan makes two references to World War I. The first (chronologically) is in his 1957 Eureka College Commencement speech:
Almost a century and a half after that day in Philadelphia, this nation entered a great world conflict in Europe. Volumes of cynical words have been written about that war and our part in it. Our motives have been questioned and there has been talk of ulterior motives in high places, of world markets and balance of power. But all the words of all the cynics cannot erase the fact that millions of Americans sacrificed, fought and many died in the sincere and selfless belief that they were making the world safe for democracy and advancing the cause of freedom for all men.
The second is in 'Encroaching Control':
The committee further said they found little evidence that any agency, bureau or department created in answer to an emergency ever went out of existence even after the emergency had disappeared. Well, an example of this could be the Spruce Products Corporation a government corporation which Congress ordered liquidated in 1920. 30 years later, it was still in existence. This was the corporation founded in World War I to secure spruce wood for airplane fuselages.