John Paul Jones spiking the cannons.

When John Paul Jones attacked Whitehaven in 1778 there were two batteries of guns to defend the town against attack from the sea. Within 6 months after the attack the number of batteries had increased to 6 and their location at either side of the harbour and on the headland made a formidable defence.
The Old Fort and the Half-moon or Lunette battery seem to have been the only major defences at Whitehaven when John Paul Jones attacked in 1778. According to him these contained about 30 guns and we know the largest of these were 42 pounders at the Old Fort and several 24 and 18 pounders probably supported these. The 42 pound guns were truly massive powerful weapons for their day capable of firing an iron ball of that weight over a mile, using 14lb of black powder as the charge, with enough force to smash open a ship’s hull. It was very cold for the time of year and in the early hours of the morning, so the guards had retired to the guardhouse at the back of the fort. They were thus easily surprised and overpowered.
However, Whitehaven was not a sleepy town but a thriving port that was already deeply involved in the war with America. Many ships had already been lost to privateers or pirates. In June of 1777 several local ships were lost to Commodore Lambert Wickes in the Reprisal accompanied by Johnson in Lexington and Nicholson in Dolphin which were causing havoc to the merchant ships in the channel between Scotland and Ireland. Whitehaven lost 4 ships in as many days.