Did a tree start World War 1?

No, it didn't. On June 28, 1914, Archduke Franz Ferdinand of Austria, the nephew of Emperor Franz Joseph and heir to the Austro-Hungarian throne, and his wife, Sophie, duchess of Hohenburg, were assassinated in Sarajevo, then part of the Austro-Hungarian Empire. The conspiracy involved Gavrilo Princip, a Bosnian Serb student. Gavrilo Princip was part of a group of fifteen assailants, who formed the Young Bosnia group, acting with support from the Black Hand, some members of which were part of the Serbian government. Following the assassination, the Austro-Hungarian government, supported by their German allies, determined to punish the Serbians for the assassination, and on July 23 sent an ultimatum to the Serbs with demands so extreme that it was expected to be rejected. The Serbians, relying on the hope of support from Russia, gave an equivocal response which led to Austrian rejection, and to a declaration of war on July 28. The Russians mobilized in support of their Serbian allies. First, this was only partial mobilization, directed against only the Austrian frontier. On July 31, after the Russian high command told the emperor that this was logistically impossible, a general mobilization was ordered. The German war plan, which relied on a quick strike against the Russians' French allies while the Russian army slowly mobilized, could not afford to allow the Russians to begin mobilization without launching their attack on the west. As such, the Germans declared war against Russia on August 1 and against France two days later, immediately launching an invasion of Luxembourg and Belgium to get around the fortifications along the Franco-German border. This violation of Belgium's neutrality led to a British declaration of war on Germany on August 4. With this declaration, five of the six great European powers became involved in the first European general war since the Napoleonic Wars. Although World War I was triggered by this chain of events unleashed by the assassination, the war's origins go deeper, involving national politics, cultures, economics, and a complex web of alliances and counterbalances that developed between the various European powers over the course of the nineteenth century, following the final 1815 defeat of Napoleon Bonaparte and the ensuing Congress of Vienna. The reasons for the outbreak of World War I are a complicated issue; there are many factors which intertwine. Some examples are: * Fervent and uncompromising nationalism * Unresolved previous disputes * The intricate system of alliances * Convoluted and fragmented governance * Delays and misunderstandings in diplomatic communications * The arms races of the previous decades. * Rigidity in military planning * Colonial rivalry * Economic rivalry The various categories of explanation for World War I correspond to different historians' overall methodologies. Most historians and popular commentators include causes from more than one category of explanation to provide a rounded account of the causal circumstances behind the war. The deepest distinction among these accounts is that between stories which find it to have been the inevitable and predictable outcome of certain factors, and those which describe it as an arbitrary and unfortunate mistake.