The Ottoman Empire joined the First World War on October 29th 1914. It was just two weeks after the Indian Division of the British army had left the port of Bombay, which was then a British colony, for Iraq as part of the "Mesopotamian Campaign". The targets of the British were the oil and gas wells on Basra coast of Iran.
The British landed on the Gulf of Basra on November 3rd 1914 and deployed in Abadan, a city in central west of Iran where oil fields are located. Two days later they seized the Al Faw Peninsula, a strategic region under the Ottoman army's control, which was used for supply and shipment. At that point, the Ottoman Empire had moved their troops to more vital fronts such as the Dardanelles, Sarikamish and Palestine. The defence of entire Iraq was left to only a small number of soldiers from the 38th Division.
The British forces entered Basra without much difficulty and captured the strategically-located Qurna region, where the Tigris and Euphrates rivers meet, on November 9th, 1914. As the Ottomans tried to form a new line of defence, the British army was making plans to seize Baghdad.
