World War 1.

Assassination of Archduke Ferdinand

Jun 28, 1914

https://www.ducksters.com/history/world_war_i/assassination_of_archduke_ferdinand.php

Austria-Hungary declares war on Serbia.

Jul 28, 1914

https://www.history.com/this-day-in-history/austria-hungary-declares-war-on-serbia

Germany Declares War on Russia.

Aug 1, 1914

https://www.rbth.com/arts/history/2017/08/01/on-this-day-germany-declared-war-on-russia_813264

Germany declares war on France.

Aug 3, 1914

https://www.historyplace.com/worldhistory/firstworldwar/index-1914.html

August 4, 1914. Britain declares war on Germany.

Aug 4, 1914

https://www.historylearningsite.co.uk/world-war-one/causes-of-world-war-one/the-british-declaration-of-war/

Austria declares war on Russia.

Aug 6, 1914

https://www.historyplace.com/worldhistory/firstworldwar/index-1914.html

Battle of Somme. Battle of Somme: The Bloodiest Military Battle.

1915

https://www.history.com/topics/world-war-i/battle-of-the-somme

The Second Battle of Ypres. The First Use of Poison Gas.

Apr 25, 1915

https://www.britannica.com/event/Second-Battle-of-Ypres

Battle of Vimy Ridge. The 3 Day Battle.

1917

https://www.history.com/topics/world-war-i/vimy-ridge-battle

signing of the treaty of Versailles

Jan 10, 1920

https://www.britannica.com/event/Treaty-of-Versailles-1919