Complex sentence: The 12th Indian Division was formed in March 1915, from units of the British Indian Army, it formed part of the Tigris Corps, for service during the Mesopotamia Campaign of the Great War.
Split into simpler sentences: The 12th Indian Division was formed in March 1915 from units of the British Indian Army. It formed part of the Tigris Corps, for service during the Mesopotamia Campaign of the Great War.