The action took place before British authorities in the Caribbean were aware that France had entered the war as an ally of the United States of America.

[citation needed] The French governor in the West Indies, François Claude Amour, marquis de Bouillé, was notified on 17 August that France was at war, and organized the invasion, infiltrating spies to rally sympathetic French-speaking Dominican support.

Following the pivotal Battles of Saratoga in October 1777 and the ensuing surrender of British General John Burgoyne's army, France decided to openly enter the American War of Independence as an ally of the young United States of America.

Operating against instructions from colonial authorities in London to minimize expenses for defence, he had pushed forward the improvement of a fort at Cachacrou and other sites.

[2] The French frigate Concorde reached Martinique on 17 August with orders from Paris to take Dominica at the earliest opportunity, and de Bouillé made immediate plans for such an operation.

He had maintained contacts in the Dominican population, which was dominated by ethnic French, including free people of color, during the years of British administration.

As a result, he had an accurate picture of the condition of the Dominican defences, and knew that the island's garrison numbered fewer than "fifty soldiers fit for duty".

The next day de Bouillé sent one of his officers to Dominica to see whether a Royal Navy frigate was still anchored in Prince Rupert's Bay (near present-day Portsmouth).

[4] Some Frenchmen (some British sources suggest they were French soldiers infiltrated onto the island) gained entry to the battery at Cachacrou that evening, plied its garrison with drink, and poured sand into the touchholes of the fort's cannons, temporarily rendering them useless.

[7] After sunset on 6 September, 1,800 French troops and 1,000 volunteers departed Martinique aboard the frigates Tourterelle, Diligente, and Amphitrite, the corvette Étourdie, and a flotilla of smaller vessels.

)[7] The first point of attack was the battery at Cachacrou, where the British garrison, befuddled by drink and with inoperative cannons, was overcome without significant resistance around dawn on 7 September.

The main force of 1,400 men was landed about 2 miles (3.2 km) south of Roseau near Pointe Michel,[1] with heavy fire from the hill batteries resulting in 40 casualties.

Considering a single ship of the line might have prevented the attack, Admiral Barrington was widely blamed for the loss, and criticized for adhering too closely to his orders.