American.
The Austo-Hungarian Empire: 1914, still alive. 1918, not still alive.
The Russian Empire: 1914, oppressing the peasants, plotting with the family, and partying at the Winter Palace till all hours. 1917, nothing.
Ever since France settled into its Third Republic, the endless fighting in post-Renaissance Europe had finally gotten a lot less fierce. Most of the rest of the Long Nineteenth Century passed relatively peacefully unless you happened to be a Boer, a Zulu, a Crimean, a Congolese, or anyone else who wasn’t actually in Europe at the time.
This peace was maintained by a series of shifting alliances maintaining a balance of power with the British dominating the seas and everyone except Italy and Russia controlling their own little colonies around the world. This was shaken to some extent by Kaiser Wilhelm’s insistence upon building a big navy but, ultimately, everyone was satisfied with the current state of affairs and the belle epoque remained fairly belle.
Then Archduke Franz Ferdinand decided to take a little trip to Sarajevo, part of the Austro-Hungarian Empire, the most ethnically diverse European political unit of the era. In plain terms, this meant the Austrians got to dominate a whole lot of other ethnic groups, including such peace-loving peoples as the Serbs and the Croats. Gavrilo Princip, a Serb, came very close to entirely failing to kill the Archduke. I mean, a fucking hand grenade didn’t even work.
In any event, that meant war. The Austro-Hungarian Empire drug the Germans in, Pan-Slavic Nationalism drug the Russians in, some damn thing or other drug the French in, and the British were sure to follow. Everyone was sure it would be over by Christmas, especially the Germans, who had a really neat plan to drive through neutral Belgium and take the French out in one knockout blow. This outraged the world, especially since there were scandalous stories about nuns being raped and babies being tossed into the air to be impaled on the Germans’ pointy helmets. The mad dashes were over by 1915 and all sides settled into trench warfare, broken by a single Christmas Truce. Sightings of a beagle flying overhead remain unconfirmed at this time.
Trench warfare means that both sides know roughly where the enemy is, and can use long-range artillery to blast and gas them, but don’t know where troops are being massed. This lead to the development of aircraft for reconnaissance, then aircraft to kill those aircraft, then aircraft to kill those aircraft, and then finally aircraft to simply drop bombs on the enemy. Meanwhile, the idea of ‘mobile cover’ matured away from the practice of carrying Burnham Wood with you into the precursor of the modern tank. However, the utterly idiotic tactics of the era meant infantrymen were still sent charging into machine gun fire and that artillery was not closely coordinated with armor or infantry, as it would be in WWII.
In 1916, a German U-Boat sunk the Lusitania, a British ship, which brought America into the war in 1917. This made perfect sense to Wilson, as he explicitly ran on a platform of keeping us out of the war in Europe. However, we would not let Theodore Roosevelt fight, because that would have been stupid. In any case, entering the war in 1917 allowed us to win a four-year war with only one year of fighting. U.S.A.! U.S.A.! U.S.A.!
Also in 1917, the Russian Empire fractured into something like clam chowder, with the Red and the White fighting for supremacy. The Reds were Soviets, advocating a Communist state, lead by Lenin, and the Whites were everyone else, advocating things from Social Democracy to Constitutional Monarchy, lead by people who would be killed or exiled. During the Revolution, soldiers stopped fighting and went back home, battleships mutinied, baby carriages rolled unimpeded down long staircases, and you, too, could have had your own Theme. Anastasia is alive and well and working on a reunion tour with Elvis, Tupac, and Black Michael Jackson.
Meanwhile in the colonies, fighting was going on as well. Japan was on the Allied side, fighting the Germans and being at least something of an asset with the understanding that it would be able to expand its empire afterwords. Bogie and Hepburn got tortured in Africa, the Chinese continued fighting their Civil War which began in 1911, and the Russians were happy they didn’t have to fight the Japanese again, seeing as how they lost to them so badly in 1909.
On the eleventh hour of the eleventh day of the eleventh month of 1918, the Armistice was signed, meaning the fierce bombardments that happened a few minutes before were forgiven and forgotten. Baldrick went home and fathered many children. Armistice Day, now called Veterans Day, became a fixed holiday, giving people the occasional Wednesday off for no reason they could discern. The War to End All Wars was over, Germany was given treaty obligations just onerous enough to piss it off but not harsh enough to keep it down entirely, France invested in a very well-defended wall, Japan got shut out of the pie-dividing almost entirely even though it was on the winning side, and America learned the Charleston, secure in its borders and prosperity.