Answer:
Competition to colonize smaller countries rose.
Countries were engaging in militarism.
Countries were splitting into alliances.
Smaller countries rose up to fight imperialism.
Explanation:
Competition to colonize smaller countries rose because some countries, like Germany and Italy believed that division of colonial power was unfair.
Countries were engaging in militarism, because they believe that a strong army makes a strong country.
Countries were splitting into alliances and the strongest one were Central Powers and Entente.
Smaller countries rose up to fight imperialism and that is why four greater empires disappeared after the war.
Poison gas was used during the war, but is not a cause of it.
Some of the major reasons why the world war I began include the following:
The Nationalist desire of the Slavic people in Austria-Hungary to be part of Serbia led to the killing of Archduke Franz Ferdinand, this contributed to why the war broke out
There was also increase in military strength of different countries in the 20th century. This increase in military strength of countries help escalate the war.
The alliance system also contributed to the breakout of the first world war because the countries involved in the war had mutual defense contracts with their allies and thus, their allied countries are bound to defend them in times of war.
Hence, we can conclude that Nationalism, alliance system, militarism as well as competition to colonize smaller countries led to the break out of world war 1.
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