Mesopotamia is the former name for modern day Iraq; an ancient name, it covers the land that runs along the Rivers Tigris and Euphrates. Why were British troops sent so far away from the Western and Eastern Fronts? The answer is oil. Britain relied heavily on oil to keep its dominant navy at sea, and moved quickly at the outbreak of war to protect its interests by occupying the oilfields and pipeline near Basra.
Like Gallipoli, conditions in Mesopotamia were awful: extremely hot temperatures (often nearing 50 degrees Celsius); arid desert and regular flooding; flies, mosquitoes and other vermin. Disease and death were rife among the British, who were unused to such conditions, and, all too often, reinforcements were only half-trained and ill-equipped. If ill or injured, men often had to spend up to two weeks on boats before reaching any kind of hospital. These factors, combined with an unexpectedly determined Turkish resistance, contributed to high casualties.
The British stayed in Mesopotamia for the length of the war, with troops seeing action particularly in 1915, January to April of 1916, and across 1917.