1. Nationalism: The early 20th century saw a rise in nationalist sentiments across Europe, where countries sought to assert their dominance and protect their own interests. This led to rivalries and tensions between nations.

2. Imperialism: European countries competed for colonies and resources around the world, often leading to conflicts and territorial disputes. These rivalries eventually escalated into a larger conflict.

3. Alliances: Various alliances had been formed between European powers, primarily for defensive purposes. However, when one country got involved in a dispute, its allies were obligated to come to its aid. This system of alliances created a domino effect, where multiple countries were drawn into the conflict.

4. Militarism: Many European countries had been engaging in an arms race, building up their militaries and stockpiling weapons. This created a readiness and willingness for war, leading to an escalation of tensions.

5. Assassination of Archduke Franz Ferdinand: The assassination of the heir to the Austro-Hungarian throne, Archduke Franz Ferdinand, by a Serbian nationalist was the immediate trigger for the war. This event prompted Austria-Hungary to issue an ultimatum to Serbia, which led to a series of diplomatic breakdowns and eventually the outbreak of war.

It is important to note that the causes of World War 1 were complex and interconnected, with multiple factors contributing to the conflict.