Complex sentence: On return to Egypt, they took part in many of the battles that formed the Sinai and Palestine Campaign, primarily as part of the Imperial Mounted Division, including the Battle of Beersheba.
Split into simpler sentences: On return to Egypt, they took part in many of the battles that formed the Sinai and Palestine Campaign, primarily as part of the Imperial Mounted Division. As part of the Imperial Mounted Division, the RGH would have been present at the Battle of Beersheba.