Causes of World War I in the context of "July Crisis"

World War I, or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers. Major areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. The war saw important developments in weaponry including tanks, aircraft, artillery, machine guns, and chemical weapons. One of the deadliest conflicts in history, it resulted in an estimated 30 million military casualties, and 8 million civilian deaths from war-related causes and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.

The causes of World War I included the rise of the German Empire and decline of the Ottoman Empire, which disturbed the long-standing balance of power in Europe, the exacerbation of imperial rivalries, and an arms race between the great powers. Growing tensions in the Balkans reached a breaking point on 28 June 1914 when Gavrilo Princip, a Bosnian Serb, assassinated Franz Ferdinand, the heir to the Austro-Hungarian throne. Austria-Hungary blamed Serbia, and declared war on 28 July. After Russia mobilised in Serbia's defence, Germany declared war on Russia and France, who had an alliance. The United Kingdom entered the war after Germany invaded Belgium, and the Ottoman Empire joined the Central Powers in November. Germany's strategy in 1914 was to quickly defeat France before transferring its forces to the east, but its advance was halted in September, and by the end of the year the Western Front consisted of a near-continuous line of trenches from the English Channel to Switzerland. The Eastern Front was more dynamic, but neither side gained a decisive advantage, despite costly offensives. Italy, Bulgaria, Romania, Greece and others entered the war from 1915 onward.

Brussels (Belgium) is considered the de facto capital of the European Union, having a long history of hosting a number of principal EU institutions within its European Quarter. The EU has no official capital but Brussels hosts the official seats of the European Commission, Council of the European Union, and European Council, as well as a seat (officially the second seat) of the European Parliament. In 2013, this presence generated about €250 million (8.3% of the regional GDP) and 121,000 jobs (16.7% of the regional employment). The main rationale for Brussels being chosen as "capital of the European Union" was its halfway location between France, Germany and the United Kingdom, the three countries whose rivalry played a role in starting the two world wars and whose reconciliation paved the way for European integration.

The National World War I Museum and Memorial is located in Kansas City, Missouri, United States. Opened in 1926 as the Liberty Memorial, it was designated by the United States Congress in 2004 as the country's official museum dedicated to World War I. In 2014, as part of the Centennial recognition, Congress added the designation as the country's official war memorial. A non-profit organization manages it in cooperation with the Kansas City Board of Parks and Recreation Commissioners. The museum focuses on global events from the causes of World War I before 1914 through the 1918 armistice and 1919 Paris Peace Conference. Visitors enter the exhibit space within the 32,000-square-foot (3,000 m) facility across a glass bridge above a field of 9,000 red poppies, each representing 1,000 combatant deaths. As of 2025, the museum’s collection includes more than 350,000 items, making it one of the largest World War I collections globally.

The museum was closed in 1994 for renovations and reopened in December 2006 with an expanded facility to exhibit an artifact collection begun in 1920.

Spain remained neutral throughout World War I between 28 July 1914 and 11 November 1918, and despite domestic economic difficulties, it was considered "one of the most important neutral countries in Europe by 1915". Spain had maintained a non-aligned stance during the political difficulties of pre-war Europe, and continued its neutrality after the war until the Spanish Civil War began in 1936. While there was no direct military involvement in the war, German forces were interned in Spanish Guinea in late 1915.

The cult of the offensive refers to a strategic military dilemma in which leaders believe that offensive advantages are so great that a defending force would have no hope of repelling the attack and therefore choose to attack. It is most often used to explain the causes of World War I and the subsequent heavy losses that occurred year after year, on all sides, during the fighting on the Western Front.

The term has also been applied to pre-World War II air power doctrine that held that "the bomber will always get through" and the only way to end a bombing campaign was to bomb the enemy into submission.

The diplomatic history of World War I covers the non-military interactions among the major players during World War I. For the domestic histories of participants see home front during World War I. For a longer-term perspective see international relations (1814–1919) and causes of World War I. For the following (post-war) era see international relations (1919–1939). The major "Allies" grouping included Great Britain and its empire, France, Russia (until 1917), Italy (from 1915) and the United States (from 1917). Opposing the Allies, the major Central Powers included Germany, Austria-Hungary, the Ottoman Empire (Turkey) and Bulgaria. Other countries (Belgium and Japan, for example) also joined the Allies. For a detailed chronology see timeline of World War I.

Non-military diplomatic and propaganda interactions among the belligerents aimed to build support for one's cause or to undermine support for one's enemies. Wartime diplomacy focused on five issues: