The siege of Pondicherry was the first military action on the Indian subcontinent following the declaration of war between Great Britain and France in the American Revolutionary War. A British force besieged the French-controlled port of Pondicherry (now Puducherry) in August 1778, which capitulated after ten weeks of siege.
Background
Following the colonial victory at Saratoga in October 1777, France decided to declare war on Great Britain as an ally to the United States. Word first reached the French Indian colony of Pondicherry in July 1778 that France and Britain had recalled their ambassadors, a sign that war was imminent. The British colonies had already received orders to seize the French possessions in India and begun military preparations.
French defenses
Pondicherry was the capital of French India and the largest of France's possessions on the subcontinent. The British would capture all of the other possessions without resistance in 1778; only Pondicherry was actively defended. The French governor, General Guillaume de Bellecombe, had at his disposal about 700 French troops and 400 sepoys (local Indian troops), and a city whose fortifications were in some disrepair. Pondicherry, as was the case with a number of other European colonial outposts in India, changed hands due to military action several times in the colonial period. Attempts to significantly improve its defences after the last round of battles in the Seven Years' War were frustrated by political infighting in the French colonial administration. In 1778 the outer works of the city were largely incomplete, with significant elements unfinished and parts of the city exposed to direct attack.
Bellecombe immediately set about improving the defences, working as quickly as possible in anticipation of British movements. Key gates were blocked, stockades and gun batteries were constructed along the shore, and anything that might give cover to the British on their advance on the defences was removed or destroyed. Bellecombe also received additional troops before the British arrived. The garrison from Karikal (which the British occupied on 10 August) add about 100 sepoys to the defence, and some of Pondicherry's inhabitants also took up arms.
A small French navy was assembled to counteract the small British navy. Admiral Tronjoli took command of the 64-gun ship of the line Brillant, the frigate Pourvoyeuse and three smaller ships, Sartine, Lawriston, and Brisson.
The siege
Preliminaries
The British colonial administration in Madras placed General Hector Munro in command of an army of nearly 20,000 men, which began arriving within a few miles of Pondicherry on 8 August. By 20 August the full army had arrived, the city was surrounded, and siege operations began.
The first noteworthy exchange between the forces was a naval encounter. Admiral Edward Vernon's fleet also consisted of five ships, carrying slightly less firepower than the French fleet. Vernon commanded the 60-gun ship of the line , and was assisted by , , , and the East India Company's ship Valentine.
In a largely inconsequential two-hour engagement in which Tronjoli was wounded, the French fleet drove Vernon away on 10 August. On 14 August French ships spotted two unknown sails; they were transport ships of the British East India Company. Their captains, apparently unaware of the hostilities, sailed before Pondicherry with British flags flying. Two of the French fleet, Pourvoyeuse and Sartine lazily gave chase. The British merchant ships escaped, but Sartine was captured when she strayed too close to the British squadron on 25 August. The loss of parity between the navies was partially made up by the arrival at Pondicherry of the 26-gun frigate Elizabeth, another private ship that had been pressed into service in the French fleet.
On 20 August, the British fleet, now six ships, appeared again. The French fleet, although it had been augmented by Elizabeth, was forced to leave Le Brisson in the harbour due to damage sustained in the first engagement, and was thus at a disadvantage. The next day, Tronjoli sailed the rest of the fleet south. Sources disagree on whether or not battle was offered or attempted on either side, but apparently no battle took place, and Tronjoli continued south. Bellecombe was surprised and dismayed to learn on 2 September that Tronjoli had sailed for Île de France, leaving Elizabeth and La Pourvoyeuse behind.