The Nicaraguan expedition of 1780 is often seen as an interesting sideline to the British war against America and her allies, a reckless adventure that destroyed a great many lives. Within the larger context of British history, the expedition has attracted attention because it involved two conspicuous characters of the century: Horatio Nelson, the hero of Aboukir Bay (1798) and then of Trafalgar (1805); and Edward Marcus Despard, the radical revolutionary hanged for treason in 1803. The fact that Nelson gave testimony on Despard's behalf at his trial, so compelling that it induced the jury to enter a plea for mercy, has inevitably led historians back to their days together on the San Juan river, when the two young men strove to accomplish an impossible mission to occupy Lake Nicaragua and split in two the Spanish empire of Central America. Yet the focus on these two men runs the danger of minimizing the logistical difficulties that the expedition encountered and of marginalizing the complexities of managing a multi-racial force that had different expectations of what was intended. For the expeditionary force that was quickly mustered to raid Spanish territory in 1780 involved British regulars, Jamaican irregulars – local militiamen, unemployed whites, privateers and slave volunteers – as well as Baymen and their slaves, and the Miskito Indians. The problems of co-ordinating this diverse crew of participants, in often unpredictable and torrential weather, must form part of the story if it is to be set within the context of eighteenth-century Caribbean expeditions.

The San Juan expedition was initiated by Governor John Dalling of Jamaica in hasty and somewhat controversial circumstances. In May 1779, Spain entered the war against Britain and along with France stretched to the limit British resources in the Caribbean. In August, Jamaica was put on a war alert when it was reported that the Count d’Estaing had sailed into Cap-François in nearby Saint Domingue with twenty-six ships of the line and more than a dozen frigates, and that 22,000 troops were massing for an invasion of Jamaica. In the event, d’Estaing left for America to help in the blockade of that coastline, but the concentration of British ships in Jamaican waters left other parts of the sprawling British territories open to attack.