On April 22, 1915, German forces shock Allied soldiers along the western front by firing more than 150 tons of lethal chlorine gas against two French colonial divisions at Ypres, Belgium. This was the first major gas attack by the Germans, and it devastated the Allied line.
https://www.history.com/this-day-in-history/germans-introduce-poison-gas
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<span>Business and industrialization centered on the cities. The ever increasing number of factories created an intense need for labor, convincing people in rural areas to move to the city, and drawing immigrants from Europe to the United States. As a result, the United States transformed from an agrarian to an urban nation, and the demographics of the country shifted dramatically.
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