Posted 26 February 2012 - 11:43 AM
I believe that the 19th Machine Gun Squadron started out as the 16th Machine Gun Squadron being redesignated around September 1917 although I am not sure of the reason for this change.
16th MGS was formed in 5th Mounted Brigade in March 1917. It was formed from machine gun sections from the Hertfordshire Yeomanry, Glasgow Yeomanry, Royal Gloucestershire Hussars, Warwickshire Yeomanry, Worcestershire Yeomanry and 2nd County of London Yeomanry.
They were initially part of the Imperial Mounted Division which was renamed the Australian Mounted Division due to the mainly Australian make up of the units.
As I said many of the 19th MGS war diaries are online and you can also look at the 16th MGS on the same site. The Australian Official History of the First World War (available on the same site) will give good information on the movements of the Australian Mounted Division and the 5th Mounted Brigade.
Hope this helps