The Great Siege of Gibraltar was an unsuccessful attempt by Spain and France to capture Gibraltar from the British during the War of the American Revolution. It was the largest battle in the war by number of combatants. On 16 June 1779, Spain entered the war on the side of France and as co-belligerents of the revolutionary United Colonies—the British base at Gibraltar was Spain's primary war aim. The vulnerable Gibraltar garrison under George Augustus Eliott was blockaded from June 1779 to February 1783, initially by the Spanish alone, led by Martín Álvarez de Sotomayor. The blockade proved to be a failure because two relief convoys entered unmolested—the first under Admiral George Rodney in 1780 and the second under Admiral George Darby in 1781—despite the presence of the Spanish fleets. The same year, a major assault was planned by the Spanish, but the Gibraltar garrison sortied in November and destroyed much of the forward batteries. The Spanish having consistently failed to either defeat the garrison or prevent the arrival of relief efforts, the besiegers were reinforced by French forces under de Crillon, who took over command in early 1782. After a lull in the siege, during which the Franco-Spanish besiegers gathered more guns, ships and troops, a "Grand Assault" was launched on 13 September 1782. This involved huge numbers—60,000 men, 49 ships of the line and 10 specially designed, newly invented floating batteries—against the 5,000 defenders. The assault proved to be a disastrous and humiliating failure, resulting in heavy losses for the Bourbon attackers. This was the largest action fought during the war in terms of numbers. The final sign of defeat for the allies came when a crucial British relief convoy under Admiral Richard Howe slipped through the blockading fleet and arrived at the garrison in October 1782. The siege was finally lifted on 7 February 1783 and resulted in a decisive victory for the British. The siege was a factor in ending the American Revolutionary War—the Peace of Paris negotiations were reliant on news from the siege, particularly at its climax. At three years, seven months and twelve days, it is the longest siege endured by the British Armed Forces. Background The Rock of Gibraltar was first fortified with the Moorish Castle in 710 AD. It was the site of ten sieges during the Middle Ages, some of them successful. An Anglo-Dutch force captured the Gibraltar peninsular in