What exactly was the action of 12 December 1782
The action of 12 December 1782 was a naval engagement fought off the coast of Spain near Ferrol, in which the British 40-gun fifth rate HMS Mediator successfully attacked a convoy of five armed ships. 

Mediator succeeded in capturing one American privateer, the Alexander, and then captured the French ex-ship of the line La Menagere. The convoy was part of Pierre Beaumarchais's supply chain to the American colonists.