Explanation

• World War I lasted from 28 July 1914 to 11 November 1918.
• It was a global war originating in Europe.
• Chlorine gas was first used during World War I at Ypres in April 1915.
• After World War I, the influenza pandemic occurred in 1918.
• During World War I, Russia signed the Peace Treaty with Germany in 1917.
• World War II started in 1939 and ended in 1945.