What was unique about world war 1

World War 1 was the first war in an industrialized age. New weapons and vehicles were used in this war that had never been used before ... WWI was the first (and only) war in which poison gas was used. The first instance when poison gas was used in the Second Battle of Ypres.

World War I proved to be the decisive break with the old world order, marking the final demise of absolutist monarchy in Europe. It would prove the catalyst for the Russian Revolution, which would inspire later revolutions in countries as diverse as China and Cuba, and would lay the basis for the Cold War standoff between the Soviet Union and the United States. The defeat of Germany in the war and failure to resolve the unsettled issues that had caused the Great War would lay the basis for the rise of Nazism, and thus the outbreak of World War II in 1939. It also laid the basis for a new form of warfare that relied heavily on technology, and would involve non-combatants in war as never before.