What were the most important reasons why World War I began? Check all that apply.• Nationalist movements were on the rise. Competition to colonize smaller countries rose. countries were engaging in militarism. countries were splitting into alliances. Countries are developing poison gas smaller countries, rows up to fight imperialism..

Answer 1

• Nationalist movements were on the rise
• Competition to colonize smaller countries rose
• Countries were engaging in militarism
• Countries were splitting into alliances