Final answer:
The primary cause of World War 1 was a combination of militarism, secret alliances, and nationalism.
Step-by-step explanation:
The primary and baseline cause of World War 1 was the combination of militarism, an arms race, and the willingness to go on the offensive. European nations at the time were heavily investing in their military forces and competing with one another for dominance. This race for military power and aggression set the stage for the outbreak of the war.
In addition to militarism, a key factor leading to World War 1 was the system of secret alliances. European powers formed alliances and pledged to support each other in the event of a conflict. When one nation was attacked, their allies felt compelled to enter the war as well, escalating the conflict.
Furthermore, the 19th-century rise in nationalism also contributed to the outbreak of the war. Nationalist sentiments were strong in many European countries, heightening tensions and creating a sense of competition between nations.
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