By the time soldiers noticed the presence of mustard gas on the battlefield, it was often too late. Fortunately, slugs could detect mustard gas well before humans could. The slugs would visibly indicate their discomfort by closing their breathing pores and compressing their bodies, and soldiers in the trenches would quickly put on their gas masks to protect themselves from harmful levels of gas. The "slug brigade" ended up saving many lives.
The Paris Gun, designed by the Germans to bombard Paris, holds an important place in the history of astronautics, as its shells were the first human-made objects to reach the stratosphere. When the guns were first employed, Parisians believed they had been bombed by a high-altitude Zeppelin, as the sound of neither an airplane nor a gun could be heard.
Many Americans were not in favor of the U.S. entering the war and wanted to remain neutral, but on April 6, 1917, the U.S. joined WWI alongside its allies--Britain, France, and Russia. Under the command of Major General John J. Pershing, more than 2 million U.S. soldiers fought on battlefields in France.
During WWI, the Turks slaughtered approximately 1.5 million Armenians out of an initial population of about 2 million. This act of genocide would later attract the attention of Hitler and was partly responsible for sowing the seeds of the Holocaust. Despite pressure from Armenians and social justice advocates, it is still illegal in Turkey to talk about what happened to Armenians during this era.
Some Americans disagreed with the United States' initial refusal to enter WWI. A group of U.S. pilots formed the Lafayette Escadrille, which was part of the French air force and became one of the top fighting units on the Western Front. It was named in honor of the Marquis de Lafayette, hero of the American and French revolutions.