The assassination of this person in 1914 triggered the chain of events that led to World War I.
Archduke Franz Ferdinand
This weapon could fire hundreds of bullets per minute and made traditional charges deadly.
Machine guns
This is the month and date when steel helmets were first introduced to WWI battlefields:
July 1915 (France, Adrian helmet)
This was first mass produced during WWI as it was essential for electrical insulation and military equipment.
Plastic
When first used in the trenches of WWI, "cooties" described this parasitic insect, one you can definitely also "catch" on an elementary school playground.
Lice
This Balkan country was supported by Russia after the assassination crisis in 1914.
Serbia
This weapon fired explosive shells over long distances and caused most battlefield deaths.
Artillery
Because many commanders misunderstood shell shock, some soldiers suffering from it were wrongly punished for this offense.
Cowardice / desertion
Blood transfusions and this medical technique that can be reconstructive or cosmetic were developed during WWI to address battlefield wounds.
plastic surgery
The term "Basket case" refers to a person that is completely helpless, incapacitated, or failing. It was first used by WWI soldiers to describe a man who had this unfortunate fate befall him:
He had all his limbs blown off (thus had to be carried by basket)
This empire declared war on Serbia in July 1914, starting the conflict.
Austria-Hungary
This terrifying weapon was first used on a large scale in 1915 and required soldiers to wear respirators.
Poison gas / chemical warfare
Experienced soldiers could tell how close these were, based on the whistle and delay before impact.
Artillery shells
First introduced during WWI, countries adopted this to conserve coal and electricity needed for the war effort by reducing the need to use lamp light.
Daylight Savings Time (DST)
Superstitious soldiers believed it was bad luck to light three of these with the same match-- the third man was sure to be killed by sniper fire.
Cigarettes
Austria-Hungary's attack on the Serbian capital of Belgrade drew this nation into the war.
Russia / Russian Empire
On average, this is how many bullets per minute a WWI machine gun could fire off.
450-600 rounds per minute
Originally called landships, these were seen on the battlefields of WWI starting in 1916 and are better known by this name meant to disguise their true purpose.
Armored tanks
At the start of the war, airplanes had no mounted weapons, so these were thrown at enemy planes during aerial combat.
bricks
During the war, Americans started calling hamburgers "liberty sandwiches" or "Salisbury steak" to avoid using words associated with this enemy:
Germany / German Empire
This nation enters the war as a result of Russia's attack on Austria-Hungary.
Germany / German Empire
This pale green gas smells of bleach and causes severe eye irritation and choking; high doses can cause death by asphyxiation (suffocation.)
Chlorine gas
Despite being badly injured, this creature saved over 200 soldiers by delivering a message containing their coordinates that stopped friendly fire from hitting a trapped unit known as the Lost Battalion in 1918.
Carrier pigeon
Injuries caused by artillery fragments called this were some of the most common wounds in WWI.
shrapnel
This phrase used today to describe going beyond limits originally referred to soldiers climbing out of trenches to attack.
Over the top / Going "over the top"
France and Britain (UK) declare war on Germany for this reason.
Germany invades the neutral kingdom of Belgium
Early airplanes were first used mainly for this purpose before aerial combat developed.
reconnaissance (scouting)
At night, enemy soldiers could be heard talking, coughing, and even crying, since the front-line trenches of both sides were only this far apart, on average:
30-100 yds. (i.e., length of a school hallway - length of a football field)
The war ended in 1918 at this oddly specific moment:
The 11th hour of the 11th day of the 11th month (Nov. 11 1918)
This phrase originally referred to the line soldiers must not cross during combat and later became a word for a time limit.
Deadline
All of the following countries were British or French colonial possessions with troops that fought in WWI except:
Thailand, Algeria, Senegal, Cambodia, Canada, Israel
Israel (note: Israel did not become a nation until 1948 - after WWII)
Engineers sometimes built fake versions of this object to hide observation posts where soldiers could spy on enemy trenches.
trees
William Frank Howard served as a British naval officer during WWI. According to Howard,
"Then we found out that some of the lads had got cigarettes; brown-looking things. They had a smoke – and I had one, and it made us all sleep. Well, of course they were coming from natives – the native crew, you see. They were selling – what do you call it—"
Marijuana
For the first time, artists were commissioned to design this to help hide artillery cannons and soldiers from enemy fire:
camoflauge
This term referencing the 1st African-American boxing champion was used by British soldiers to describe the powerful German artillery shells.
Jack Johnson