Answer:
1- New offensive weapons were implemented during the war including tanks and poison gases. In 1915, the Germans used poison gases against the Allies fighting in the trenches on the Western Front. To protect soldiers from chemical warfare, gas masks were developed.
2- The publication of the Zimmermann Telegram and the escalation of German submarine attacks on US merchant vessels led the US Congress to declare war on Germany on April 6, 1917. More than 1.3 million men and twenty thousand women enlisted in the armed forces.
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