1. Austria-Hungary's Declaration of War: The immediate cause of World War I was the declaration of war by Austria-Hungary against Serbia on July 28, 1914. Austria-Hungary took this step after the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, by a Serbian nationalist. As a result, most historians place considerable blame on Austria-Hungary for starting the war.
2. Germany's "Blank Cheque": Germany's full support of Austria-Hungary in the July Crisis, when Russia started to mobilize its military, is often seen as a critical factor in the outbreak of the war. Germany's assurance of backing to Austria-Hungary, known as the "blank cheque," allowed Austria-Hungary to take reckless actions without fear of Russian intervention.
3. Schlieffen Plan: Germany's military strategy, the Schlieffen Plan, was based on the idea of a swift victory over France, followed by a rapid redeployment of troops to the eastern front to confront Russia. This strategy required an invasion of Belgium, which had pledged neutrality in international treaties. The German invasion of Belgium brought Britain, committed to honoring the Belgian neutrality treaties, into the war.
4. Violation of Belgian Neutrality: The invasion of Belgium, a neutral country, was widely condemned as a breach of international law. It provided a moral justification for Britain and other Allied powers to declare war on Germany. The violation of Belgium's neutrality is often cited as a central reason for Germany being blamed for starting the war.
5. Influence on Austria-Hungary: Germany strongly influenced Austria-Hungary's foreign policy and decision-making during the July Crisis. Some historians argue that Germany, seeking to support and strengthen its ally, encouraged Austria-Hungary's aggressive actions against Serbia, knowing the risk of a wider conflict.
6. Public Perception: In the aftermath of the war and following the release of certain diplomatic documents, public perception in many Allied countries was shaped to view Germany as the main aggressor and warmonger. This narrative, promoted by wartime propaganda and post-war sentiment, persists in popular understandings of the war's origins.
It's important to note that not all historians agree that Germany was solely responsible for starting World War I. Some argue that the conflict resulted from a complex web of factors involving geopolitical rivalries, nationalism, and alliances among the major European powers. The historiographical debate surrounding Germany's responsibility and the relative culpability of other nations continues, and different interpretations of the evidence continue to shape our understanding of the origins of World War I.