when did the battle start?
20–27 August 1810
Battle of Grand Port
 The battle was fought during 20–27 August 1810 over possession of the harbour of Grand Port on Isle de France (now Mauritius) during the Napoleonic Wars. 
where was the battle of grand port fought? Indian Ocean
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Battle of Grand Port [SEP] Introduction
The Battle of Grand Port was a naval battle between squadrons of frigates from the French Navy and the British Royal Navy. The battle was fought during 20–27 August 1810 over possession of the harbour of Grand Port on Isle de France (now Mauritius) during the Napoleonic Wars. The British squadron of four frigates sought to blockade the port to prevent its use by the French through the capture of the fortified Île de la Passe at its entrance. This position was seized by a British landing party on 13 August and, when a French squadron under Captain Guy-Victor Duperré approached the bay nine days later, the British commander, Captain Samuel Pym, decided to lure them into coastal waters where his superior numbers could be brought to bear against them.