The Action of 13 March 1806 was a naval engagement of the Napoleonic Wars, fought when a British and a French squadron met unexpectedly in the mid-Atlantic. Neither force was aware of the presence of the other prior to the encounter and were participating in separate campaigns. The British squadron consisted of seven ships of the line accompanied by associated frigates, led by Rear-Admiral Sir John Borlase Warren, were tasked with hunting down and destroying the French squadron of Contre-Admiral Jean-Baptiste Willaumez, which had departed Brest for raiding operations in the South Atlantic in December 1805, at the start of the Atlantic campaign of 1806. The French force consisted of one ship of the line and one frigate, all that remained of Contre-Admiral Charles-Alexandre Durand Linois' squadron that had sailed for the Indian Ocean in March 1803 during the Peace of Amiens. Linois raided British shipping lanes and harbours across the region, achieving limited success against undefended merchant ships but repeatedly withdrawing in the face of determined opposition, most notably at the Battle of Pulo Aura in February 1804. With his stores almost exhausted and the French ports east of the Cape of Good Hope that could have offered him replenishment eliminated, Linois decided to return to France in January 1806, and by March was inadvertently sailing across the cruising ground of Warren's squadron.