The Samarra offensive (March 13 – April 23, 1917) was launched by the British against the Ottomans as part of the Mesopotamian Campaign in World War I. After Baghdad fell to the British on March 11, 1917, there were still 10,000 Ottoman troops north of the city, led by Khalil Pasha, who could represent a threat to Anglo-Indian forces. Furthermore, another 15,000 Ottomans under Ali Ihsan Bey were being driven out of Persia by the Russians, and were attempting at joining Khalil's forces in northern Iraq.