World War I

World War I was a major conflict fought over four years from 1914 to 1918, mainly in continental Europe.

Origin
It was caused in part by the influence of the Nemesis statue passing by Earth in 1913. (DW: Silver Nemesis)

Foreshadowing
In 1903, after receiving a wealth of information from the future, Grigori Rasputin foresaw the great war. (CC: The Wanderer) The time-traveling Family of Blood, while in 1913, warned some people there would be a war the next year. (DW: The Family of Blood)

The War
Some of the battlegrounds were Passchendaele, the Somme and Gallipoli. (DW: The Sea Devils, TW: To the Last Man) A million British soldiers died during the war. (TW: To the Last Man)

In 1915, the RMS Lusitania was sunk, precipitating the United States getting involved. (BFA: The Sirens of Time)

The immortal Jack Harkness fought in the war (DW: Utopia, IDW: The Forgotten), as did Tim Latimer and Hutchinson. (DW: The Family of Blood) Tommy Brockless also served, and was eventually executed in 1918 when, suffering from shell shock, he refused to return to the front lines. (TW: To the Last Man) Solomon and the older members of his Hooverville fought in "the Great War," (DW: Evolution of the Daleks) as did Diagoras. (DW: Daleks in Manhattan)

Several soldiers were kidnapped by the War Lords for their War Games. They were eventually returned home by the Time Lords. (DW: The War Games)

The Doctor visited the war several times. The First Doctor along with Susan, survived a Zeppelin air raid. (DW: Planet of Giants) In 1914, the Third Doctor, Tobias Philby and Thomas ended up in a No Man's Land in France, where they learned of a German artillery build-up and warned the British Army of it. (TVC: The Amateur)

The Third Doctor also claimed to have been wounded at Gallipoli. (DW: The Sea Devils) The Seventh Doctor offered one private the opportunity to travel with him, but he declined. (BE: Front Line)

The Ninth Doctor again visited the war, this time at. He went there with Rose Tyler and started the football game between the opposing troops taking part in the truce. (IDW: The Forgotten)

The Tenth Doctor and Rose visited the war again and put a stop to the Warfreekz' observation of the battles. (DWA: Warfreekz!)

After the war, an influenza pandemic raged across the world. The Ice Warriors had released the virus to weaken humanity and allow them to invade. The virus killed the Ice Warriors instead. (DWS: Cold)

The Proamonians wore spiked helmets like those the German soldiers wore during the war (DW: Dragonfire) as did the Vykoids. (NSA: The Forgotten Army)

Second World War
The war was followed by a Second World War which began in 1939. (DW: The Empty Child/The Doctor Dances, Victory of the Daleks et al)