World War I, Mesopotamia, 1914–April 1916

The British occupation of Basra, Turkey's port at the head of the Persian Gulf, in November 1914 had been justifiable strategically because of the need to protect the oil wells of southern Persia and the Abadan refinery. The British advance of 46 miles northward from Basra to al-Qurnah in December and the further advance of 90 miles up the Tigris to al-'Amarah in May–June 1915 ought to