Although Italy had been allied with the German and Austro-Hungarian Empires since 1882 as part of the Triple Alliance, the nation had its own designs on Austrian territory in Trentino, Istria and Dalmatia. Rome had a secret 1902 pact with France, effectively nullifying its alliance. At the start of hostilities, Italy refused to commit troops, arguing that the Triple Alliance was defensive in nature, and that Austria-Hungary was an aggressor. The Austro-Hungarian government began negotiations to secure Italian neutrality, offering the French colony of Tunisia in return. However, Italy then joined the Entente in April 1915 and declared war on Austria-Hungary in May. Fifteen months later, it declared war on Germany. Faced with Russia, Austria-Hungary could spare only one third of its army to attack Serbia. After suffering heavy losses, the Austrians briefly occupied the Serbian capital, Belgrade, but counterattacks had succeeded in driving them from the country by the end of 1914. The Serbs suffered defeat near modern day Gnjilane in Kosovo, forces being evacuated by ship to Greece.
In late 1915 a Franco-British force landed at Salonica in Greece, to offer assistance and to pressure the government to declare war against the Central Powers. Only at the end of the conflict were the Entente powers able to break through, which was after most of the German and Austro-Hungarian troops had been withdrawn. With the aid of numerous black and white and colour photographs, many previously unpublished, the History of World War I series recreates the battles and campaigns that raged across the surface of the globe, on land, at sea and in the air.