Harry meets a woman and baby. He claims to know her. He reminds her of the day "you wore the gown of green." He has returned from Portugal and Spain with gold and a pension, though he has lost a limb "saving my commander's life." He proposes.
The opening line makes Harry either a soldier or a sailor.
Roud assigns the same number to "The Gown of Green" (I) and (II). The two seem related though there is no overlap in story or evidence that they are fragments of some longer ballad; in fact, the wars are not the same. - BS
(In fact it's just possible that they are the same, though not likely. During the American Revolutionary War, Spain was fighting against Britain; if the hero was a sailor, or just a soldier being transported in a warship, it's just possible that he could have been in a fight with a Spaniard. Alternately, if we reverse the place where he lost the limb, Our Hero could have fought in Wellington's Peninsular Campaign in Spain, then been shipped to America to fight in the War of 1812. That happened to several regiments. - RBW)