In World War I, one out of three English males between 17 and 35 years of age was killed. (source)

At the outbreak of the First World War, the American air force comprised only fifty men. (source)

On July 1, 1916, the British army sustained 60,000 casualties in a single day at the Battle of the Somme.

During World War I, the wife of U.S. President Woodrow Wilson grazed sheep on the front lawn of the White House. (source)

Pope John XXIII had served as a sergeant in the Italian army during World War I. (source)

In the First World War, during Christmas 1914, along many areas of the Western Front, many German and British soldiers stopped fighting each other and mingled with each other, exchanging food and small gifts. Some even sung carols or played soccer together.

During World War I, a gun was invented by Jones Wister that could shoot around corners. It was never used, but a similar gun was used by Germans in World War II.

At the end of 1914, when Russia was fighting in World War I, the Russian Army had 6,553,000 men, but only 4,652,000 rifles.

World War I was called "World War I" as early as 1919, 20 years before World War II began. (source)

The French towns of Bezonvaux, Beaumont-en-Verdunois, Cumières-le-Mort-Homme, Fleury-devant-Douaumont, Haumont-près-Samogneux and Louvemont-Côte-du-Poivre have a mayor and a municipal council, even though they were all destroyed in the First World War and have been unoccupied since.

During World War I, in 1916, the Titanic's sister ship, the Britannic, was torpedoed and sank. Although it sank in about the same amount of time that it took the Titanic to sink, only 30 lives were lost because regulations had since been changed to ensure that there was a lifeboat seat for every passenger. (source)

In 1916, at the Battle of Verdun, a single German soldier took Fort Douaumont from the French after the French General Chrétien failed to pass on a message. His orders were to defend the fort to the last man, but when he went on leave he failed to inform his successor, resulting in the fortress being manned by just a few gunners who were taken completely by surprise. (source)

Violet Jessup, a stewardess on the Titanic, survived its sinking. She also survived the sinking of the Britannic in 1916, and she was aboard the Olympic when it was rammed in 1911.

In 1916, Woodrow Wilson successfully campaigned for re-election as president with slogans such as "He Kept Us Out of War," and "War in Europe—Peace in America." Five months after the election, in April 1917, Wilson led the United States into World War I. (source)

During the 19^th century, Turkey lost three wars to Russia (in 1812, 1829, and 1878). The Greeks won their independence by defeating the Turks in 1827, while the Egyptians invaded and defeated Turkey in wars fought in 1832, 1839, and 1840. From 1912 to 1913, Turkey lost wars to Italy, Greece, Serbia, Bulgaria, and Albania. During World War I, Turkey joined the Central Powers and went down to defeat with Germany. (source)

Winnie-the-Pooh is based on a real bear. On August 24th, 1914, a Canadian soldier and veterinarian named Harry Colebourn, en route to a training camp in Valcartier, Quebec, purchased an orphaned black bear cub for $20 in White River, Ontario, which he named Winnipeg, or Winnie for short. When his unit was sent over to France during World War I, Colebourn loaned her to the London Zoo, intending to take her back to Canada after the war. However, Winnie's gentle disposition made her the zoo's top attraction, and on December 1, 1919, he donated her to the zoo. In the mid 1920s, writer A. A. Milne often took his young son, Christopher Robin, to the zoo, and Christopher named his teddy bear "Winnie-the-Pooh" after Winnie. A. A. Milne went on to write several best-selling children's books about Christopher Robin and Winnie-the-Pooh.