My book on Robert Forrester mentioned several pieces of evidence hinting that he may have been a soldier in the American War of Independence. For example, he was in the company of a Chelsea pensioner when arrested, and he owned a gun in NSW at a time this was rare and he could shoot straight.
Recently, when in England, I made a brief visit to the Public Records Office at Kew to research various matters. Re Robert Forrester, I found nothing which suggested he had ever been a soldier - at least nothing indexed with his name or its variations.
The British Army Service Records, 1760-1915, on the Find-My-Past website also make no mention of a relevant Robert.
This does not mean conclusively that the soldier theory is false - only that the means of proving it remain very limited. But being unable to trace his whereabouts prior to 1783 does mean that finding his place of origin remains elusive.