The Battle of Jebel Hamlin was a British-led attempt to encircle 15,000 Turkish troops led by Ali Ishan Bey as they retreated from Persia en route to meet up with regional Turkish Commander-in-Chief Khalil Pasha.
The battle was part of the March-April 1917 Samarrah Offensive, which was primarily aimed at capturing the Turkish railway at Samarrah.
General Keary led an Anglo-Indian force of 8,000 men to prevent Ali Ishan Bey's force of 10,000 men from rendezvousing with Khalil's main force of 10,000 men retreating north from Baghdad. Ishan was retreating from Persia as a result of Russian operations in March.
The British expected Ishan to attempt to meet up with Khalil's force at Baquba, where a Turkish garrison was in place. As a result, Keary's force was dispatched on March 14 with Baquba in mind. However, on March 17, the garrison at Baquba began to withdraw north to meet up with Ishan.
Major General Keary, hoping to trap Ali Ishan Bey's 15,000 Turkish troops between his own forces and those of the Russian-Persian force, marched towards their new position at the foot of the Jebel Hamlin mountains.
However, he was unaware that the February Revolution had broken out in Russia, halting all Russian military operations in Persia. As a result, Keary's forces were the only ones pursuing Ishan, which had significant consequences.
While 4,500 Turkish troops dug secure lines on high ground behind two canals, Keary's preparations to storm the lines were not undertaken in secrecy.
As a result, when the British attack finally began on March 25, the Turkish defense was well prepared. The attack was a failure, and the British suffered 1,200 casualties.
Ishan's force managed to escape southwest, headed for Turkish forces on the Tigris River.