The speaker is, I’m pretty sure, one of the many young Irishmen known as the Wild Geese who enlisted into the French army in the belief that Bonaparte was at heart a revolutionary who would eventually liberate Ireland from British rule.

Events in the song are not chronological. The Mamelukes were defeated at the Battle of the Pyramids in 1798. Marengo was in 1800 in northern Italy against the Austrians. Old Frederick is probably Frederick William III of Prussia, who was soundly defeated at Jena in 1806. However, the royal family were not ‘sheltered’ by Bonaparte but fled to Russia. Vienna was taken in late 1805, not 1806 as the song says.

‘Beltona’ should perhaps be ‘Bellona’, goddess of war.

In his book ‘The Green Linnet’ Peter Wood says that Bonaparte was so-called because he habitually wore a green coat.

I think it was Kevin Conneff who sang some verses of the song on the Chieftains ‘Bonaparte’s Retreat’.