Complex sentence: In January 1921 Mesopotamian Group was formed by raising Mesopotamian Wing to group status and on 1 October 1922 Mesopotamian Group was absorbed into the newly formed Iraq Command which was given control of all British forces in Iraq.
Split into simpler sentences: In January 1921 Mesopotamian Group was formed by raising Mesopotamian Wing to group status. The following year, on 1 October 1922 Mesopotamian Group was absorbed into the newly formed Iraq Command which was given control of all British forces in Iraq.