On the 28th of June 1914, Archduke Franz Ferdinand of Austria visited Sarajevo. Gavrilo Princip stood in the street where his car turned. He fired two pistol shots that fatally wounded the heir to the Austro-Hungarian throne and his wife Sophie. This single act triggered a month of diplomatic maneuvering known as the July Crisis. Austria-Hungary declared war on Serbia on the 28th of July after issuing an ultimatum with ten demands. Russia mobilized in support of Serbia. Germany then declared war on both Russia and France. The United Kingdom entered the conflict when German forces invaded Belgium.
The web of alliances had been tightening for decades before this moment. In 1873, Otto von Bismarck negotiated the League of the Three Emperors including Austria-Hungary, Russia, and Germany. By 1890, Kaiser Wilhelm II refused to renew the Reinsurance Treaty with Russia. This allowed France to form the Franco-Russian Alliance in 1894. Britain later joined through the Entente Cordiale in 1904 and the Anglo-Russian Convention in 1907. These agreements created the Triple Entente opposing the Triple Alliance between Germany, Austria-Hungary, and Italy.
An arms race intensified these tensions. Admiral Alfred von Tirpitz sought to build an Imperial German Navy capable of competing with the British Royal Navy. The launch of HMS Dreadnought in 1906 made every existing battleship obsolete. Despite vast spending, Germany never achieved naval superiority. Military spending by six major European powers increased by over 50% from 1908 to 1913. Tensions in the Balkans reached a breaking point as Austria annexed Bosnia and Herzegovina in 1908.
Trench Warfare And Technology
By the end of 1914, opposing forces confronted each other along an uninterrupted line of entrenched positions stretching from the Channel to the Swiss border. Both sides struggled to develop tactics for breaching these defensive systems without heavy casualties. On the 22nd of April 1915 at the Second Battle of Ypres, Germans used chlorine gas for the first time on the Western Front. This violated the Hague Convention but marked a new era of chemical warfare.
The Battle of Verdun lasted from February to December 1916. Casualties exceeded 700,000 between the two combatants. Verdun became a symbol of French determination and self-sacrifice. The Battle of the Somme ran from July to November 1916. Its opening day on the 1st of July 1916 was the bloodiest single day in British Army history with 57,500 casualties including 19,200 dead. As a whole, the offensive led to an estimated 420,000 British casualties alongside 200,000 French and 500,000 German losses.
New technologies emerged to break the stalemate. Tanks appeared on the battlefield though they remained unreliable. Aircraft carriers made their first combat use when HMS Furious launched Sopwith Camels against Zeppelin hangars at Tondern in July 1918. Blimps conducted antisubmarine patrols while machine guns dominated the landscape. Diseases like trench foot, lice, typhus, and Spanish flu killed as many soldiers as enemy fire.