The Battle of Grand Port was fought on 20–27 August 1810 in the harbour of Grand Port between the British and French navies over the harbour of Grand Port as part of the Mauritius campaign of 1809–1811. A British squadron of four frigates under Captain Samuel Pym sought to blockade Grand Port in the French colony of Isle de France by capturing the fortified Île de la Passe at the port's entrance. The position was seized by a British landing party on 13 August, and when a French squadron under Frigate Captain Guy-Victor Duperré approached the bay nine days later, Pym decided to lure them into coastal waters where his forces could ambush them.
Most of Duperré's squadron managed to break past the British blockade and take shelter in the protected anchorage, which was only accessible through a series of complicated routes between reefs and sandbanks that were impassable without an experienced harbour pilot. When Pym ordered his frigates to attack the French warships on 22 and 23 August, his ships became trapped in the narrow channels of the bay: two were irretrievably grounded, a third struck her colours after being outnumbered and a fourth was unable to close to within effective gun range. Although the French ships were also badly damaged in the exchange of gunfire, the battle was a disaster for the British: one ship was captured after suffering irreparable damage, the grounded ships were scuttled to prevent their capture by French boarding parties and the remaining frigate was seized as it left the harbour by the main French squadron from Port Napoleon under Commodore Jacques Hamelin.
The battle was one of the worst defeats suffered by the British navy during the Napoleonic Wars, and left Britain's vital trade convoys in the Indian Ocean exposed to attack from Hamelin's ships. In response, the British reinforced their squadron on Isle Bourbon under Commodore Josias Rowley by ordering all available ships to the region, but this piecemeal reinforcement resulted in a series of desperate actions as individual British ships were attacked by the confident and more powerful French squadron. In December an adequate reinforcement was assembled with the provision of a strong squadron under Admiral Albemarle Bertie, which rapidly invaded and captured Isle de France.
Background
During the early 19th century, the Indian Ocean formed an essential part of the network of trade routes that connected the British Empire. Heavily laden East Indiamen travelled from ports in British India such as Bombay and Calcutta to Britain carrying millions of pounds of goods. From Britain, the ships returned on the same routes, often transporting recruits for the growing Presidency armies, which were under the control of the East India Company (EIC). Following the outbreak of the Napoleonic Wars in 1803, the British Admiralty had made the security of these routes a priority, resulting in Britain occupying the Dutch Cape Colony and destroying the Dutch navy squadron in Java between 1806 and 1807. The two main French colonies in the Indian Ocean, Isle Bonaparte and Isle de France, were more complicated targets, protected from attack not only by the great distances involved in preparing an invasion attempt but also by heavy fortifications and substantial French Imperial Army garrisons augmented by large colonial militias.
The French had recognised the importance of these islands as bases for raiding warships during the French Revolutionary Wars, but by late 1807 the only naval resources allocated to the region were a few aging frigates and a large number of local privateers. Following the reduction of these remaining naval forces on Isle de France by defeat in battle and disarmaments due to age and unseaworthiness during 1808, the French Imperial Navy made a serious attempt to disrupt British trade in the region, ordering five large modern frigates to sail to Isle de France under Commodore Jacques Félix Emmanuel Hamelin. Four of these ships broke through the British blockade of the French coast, arriving in the Indian Ocean in the spring of 1809, where Hamelin dispersed them into the Bay of Bengal with orders to intercept, attack, and capture or destroy the heavily armed but extremely valuable convoys of East Indiamen. The first French success came at the end of the spring, when the frigate Caroline successfully attacked a convoy in the action of 31 May 1809, seizing two heavily laden merchant ships.
Commodore Josias Rowley was given command of the British response, a hastily assembled force composed mainly of those ships which happened to be available at the Cape of Good Hope in early 1809. Ordered to stop the French raiders, Rowley was unable to spread his small squadron wide enough to pursue the roving French frigates, instead using his forces to blockade and raid the French islands in anticipation of Hamelin's return. In August, Caroline arrived with her prizes at Saint-Paul on Isle Bonaparte and Rowley determined to seize the frigate. He planned a successful invasion of the town, launched on 20 September, which resulted in the capture of the port's defences, Caroline, and the captured East Indiamen. With his objectives complete, Rowley withdrew five days later. Almost a year later, Rowley returned with a larger task force and made a second landing around the capital of Isle Bonaparte, Saint-Denis. Marching on the seat of government, Rowley's troops rapidly overwhelmed the defences and forced the island's garrison to surrender, renaming the island Isle Bourbon and installing a British governor.
Hamelin had used the British preoccupation with Isle Bonaparte to send additional frigates to sea during 1809 and early 1810, including his flagship Vénus, which captured three East Indiamen in the action of 18 November 1809, and Bellone, which took the Portuguese frigate Minerva in the Bay of Bengal a few days later. Minerva, renamed Minerve in French hands, was subsequently involved in the action of 3 July 1810, when a further two East Indiamen were captured. The squadron in this action was commanded by Guy-Victor Duperré in Bellone, whose ships were so badly damaged that Duperré was forced to spend nearly a month repairing his vessels in the Comoros Islands before they were ready to return to Isle de France.
Operations off Grand Port
With Isle Bourbon secured in July 1810, the British now occupied a large fortified island base within easy sailing distance of Isle de France. Even before Isle Bourbon was completely in British hands, Rowley had detached HMS Sirius from the invasion squadron with orders to restore the blockade of Isle de France. Shortly afterwards, Captain Samuel Pym of HMS Sirius led his men in a raid on a coastal vessel moored off the southern side of the island. Two days after this successful operation, British reinforcements arrived in the form of the frigates HMS Iphigenia and HMS Nereide, and the small brig HMS Staunch. Nereide carried 100 specially selected infantrymen from the 69th and 33rd Regiments and some artillerymen from the garrison at Madras to be used in storming and garrisoning offshore islands, beginning with Île de la Passe, a heavily fortified islet off the southeastern shore which protected the entrance to the natural harbour of Grand Port. These fortified islands could be used to block entry to the ports of Isle de France and thus trap Hamelin's squadron.
Grand Port was an easily defensible natural harbour because the bay was protected from the open sea by a large coral reef through which a complicated channel meandered, known only to experienced local pilots. Île de la Passe was vitally important in the control of Grand Port because it was equipped with a heavy battery that covered the entrance to the channel, thus controlling the passage to the sheltered inner lagoon. The British planned to use the troops on Nereide, under her captain Nesbit Willoughby, to storm Île de la Passe and capture the battery. Willoughby would then use a local man serving on his ship named John Johnson (referred to in some texts as "the black pilot"), to steer through the channel and land troops near the town, distributing leaflets promising freedom and prosperity under British rule in an attempt to corrode the morale of the defenders.
The first attack on Île de la Passe was launched on the evening of 10 August, with Staunch towing boats carrying over 400 soldiers, Royal Marines, and volunteer sailors to the islet under cover of darkness, guided by Nereide's pilot. During the night the pilot became lost; the boats were scattered in high winds and had not reassembled by dawn. To distract French attention from the drifting boats, Pym directed Captain Henry Lambert in Iphigenia to sail conspicuously off Port Napoleon, where the main body of the French squadron, led by Hamelin in Vénus, was based. Pym joined Lambert later in the day and the frigates subsequently returned to the waters of Grand Port by different routes, confusing French observers from the shore as to British intentions. By 13 August, the boats originally intended for the attack had still not been assembled and Pym decided that he could not risk waiting any longer without the French launching a counterattack. Launching his own boats at 8:00 pm, guided by the pilot and commanded by Pym's second-in-command, Lieutenant Norman, Pym's marines and sailors landed on the island in darkness under heavy fire from the defenders. Norman was killed in the initial exchange of fire, but his deputy, Lieutenant Watling, seized the island by storming the fortifications surrounding the battery. Seven British personnel were killed and 18 wounded in the battle, in which the storming party managed to seize intact French naval code books and took 80 prisoners. Willoughby was furious that Pym had assumed command of the operation without his permission and the officers exchanged angry letters, part of an ongoing disagreement between them that engendered mutual distrust.
With Île de la Passe secure, Pym gave command of the blockade of Grand Port to Willoughby and returned to his station off Port Napoleon with Iphigenia. Willoughby used his independent position to raid the coastline, landing at Pointe du Diable on 17 August on the northern edge of Grand Port with 170 men and storming the fort there, destroying ten cannon and capturing another. Marching south towards the town of Grand Port itself, Willoughby's men fought off French counterattacks and distributed propaganda pamphlets at the farms and villages they passed. Willoughby re-embarked his troops in the evening but landed again the following day at Grande Rivière to observe the effects of his efforts. Burning a signal station, Willoughby advanced inland, but was checked by the arrival of 800 French reinforcements from Port Napoleon and returned to HMS Nereide. The brief expedition cost the British two men wounded and one missing, to French casualties of at least ten killed or wounded. Willoughby followed the attack on Grande Rivière with unopposed minor landings on 19 and 20 August.
Duperré's arrival
Willoughby's raiding was interrupted at 10:00 am on 20 August when five ships were sighted, rapidly approaching from the southeast. These ships were Guy-Victor Duperré's squadron of Bellone, Minerve, the corvette Victor, and prizes Windham and Ceylon returning from the Comoros Islands. Following a month of repairs on Anjouan, Duperré had sailed for Isle de France without encountering any opposition on his return passage, and was intending to enter Grand Port via the channel protected by Île de la Passe. Duperré was unaware of the British occupation of the island, and Willoughby intended to lure the French squadron into the channel by concealing the British presence off the harbour. Once there, Willoughby hoped to defeat them or damage them so severely that they would be unable to break out unaided, thus isolating Duperré's squadron from Hamelin's force in Port Napoleon and containing the French in separate harbours to prevent them from concentrating against the British blockade squadrons. Willoughby brought Nereide close to Île de la Passe to combine their fire and protect his boats, which were carrying 160 men back to Nereide from a raid near Grand Port that morning.
Raising a French tricolour over Île de la Passe and on Nereide, Willoughby transmitted the French code captured on the island: "L'ennemi croise au Coin de Mire" and received an acknowledgement from Duperré. The use of these signals convinced Duperré, over the objections of Captain Pierre Bouvet on Minerve, that Néréide was Surcouf's privateer Charles, which was expected from France. The French squadron closed with the harbour during the morning, Victor entering the channel under Île de la Passe at 1:40 pm. As Victor passed Néréide and the fort, Willoughby opened fire, Lieutenant Nicolas Morice surrendering the outnumbered corvette after the first volley. Willoughby sent boats to attempt to take possession of Victor, but they were unable to reach the vessel. Behind the corvette, Minerve and Ceylon pushed into the channel and signalled Morice to follow them, exchanging fire with the fort. As Morice raised his colours again and followed Minerve, a large explosion blasted out of Île de la Passe, where the false French flag had ignited on a brazier as it was lowered and set fire to a nearby stack of cartridges, which exploded in the close confines of the fort. Three men were killed and 12 badly burned, six cannon were dismounted and one discharged unexpectedly, killing a British sailor in a boat attempting to board Victor. With the fort out of action and a significant number of her crew scattered in small boats in the channel, Néréide was alone and unable to block French entry to Grand Port.