[19] The vulnerable Gibraltar garrison under George Augustus Eliott was blockaded from June 1779 to February 1783,[20] initially by the Spanish alone, led by Martín Álvarez de Sotomayor.

After the Spanish 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.

The final sign of defeat for the besiegers came when a crucial British relief convoy under Admiral Richard Howe slipped through the blockading fleet and arrived at the garrison in October 1782.

On 12 April 1779 France signed the Treaty of Aranjuez with Spain based on its Third Pacte de Famille between the Bourbon kings, wherein they agreed to aid one another in recovering lost territory from Britain.

The main physical task facing Eliott was an extensive building programme of new fortifications for Gibraltar, as set out in a report by a commission that had examined the state of the Rock's defences in the early 1770s.

The most prominent new work was the King's Bastion designed by Sir William Green and built by the Soldier Artificer Company on the main waterfront of the town in Gibraltar.

[40] The King's Bastion comprised a stone battery holding 26 heavy guns and mortars, with barracks and casemates to house a full battalion of foot.

The Royal Navy had only a token force present—mostly sailors and marines on shore—but one former ship of the line, HMS Panther, was moored in the harbour as a hulk and floating battery.

[43] Britain stepped up preparations after France entered the conflict in 1778, although the French were initially more concerned with sending forces to America, and it was not until Spain joined the war that the long-expected siege commenced.

The combined Spanish and French fleets blockaded Gibraltar from the sea, while on the land side an enormous army constructed forts, redoubts, entrenchments, and batteries from which to attack.

They had also repulsed several small testing assaults made by the Spanish and had great faith that they would receive supplies by sea, thus enduring the cold and hunger.

[48] The Spanish were forced to commit a greater number of troops and ships to the siege, postponing the planned invasion of England, owing to this and the cancellation of the Armada of 1779.

While the two sides unceasingly exchanged shot and shell, by the end of the summer provisions once again began to run low, and scurvy started to reappear thus reducing the effective strength of the garrison.

A badly wounded Spanish artillery officer, José de Barboza, refused to be moved; Elliot tried to persuade him, but he asked to be "left alone and perish amid the ruin of my post."

[64] With all the Spanish forward positions secured, the British set upon the destruction of provisions, ammunition, weapons, and defensive structures, taking booty and spiking the guns.

Portuguese vessels with lemons, wine and vegetables helped the garrison, and gave valuable intelligence on the Spanish lines and the heavy casualties suffered from the British guns.

[23] John Jay the American peace commissioner during the negotiations realised the importance of the Gibraltar siege and the impending plan by France and Spain to capture the Rock.

Elliot suggested to his artillery general Boyd to bombard the lines with red-hot shot and grapeshot, which had been used to great effect against Spanish gunboats daring to come close enough to make an attack.

[87] The French engineer Jean Le Michaud d'Arçon invented and designed the floating batteries—'unsinkable' and 'unburnable'—intended to attack from the sea in tandem with other batteries bombarding the British from land.

The floating batteries would have strong, thick wooden armour—one-metre-wide (3 ft) timbers packed with layers of wet sand, with water pumped over them to avoid fire breaking out.

[82] On 13 September 1782 the Bourbon allies launched their great attack: 5,260 fighting men, both French and Spanish, aboard ten of the newly engineered 'floating batteries' with 138[89] to 212 heavy guns under the command of Don Buenaventura Moreno.

[100] During this operation, Roger Curtis, the British naval commander, seeing the attacking force in great danger, warned Elliot about the huge potential death toll and that something must be done.

[102] British marines and sailors then stormed the Pastora, taking the men on board as prisoners and eventually pulled them off the doomed ship, having also seized the Spanish Royal Standard which had been flying from the stern.

[102] The rest of the Spanish batteries blew up in similar horrific style; the explosions lofted huge mushroom clouds that rose nearly 1,000 feet in the air.

[109] The French had done all they could to help the Spanish achieve their essential war aim, and began serious discussions on alternative exit strategies, urging Spain to offer Britain some very large concessions in return for Gibraltar.

[125] With Gibraltar safe, along with Rodney's victory at the Battle of the Saintes back in April, British demands at the peace talks had now greatly strengthened, undermining the French confidence that had greeted the success at Yorktown.

Four days later a Spanish vessel flying a flag of truce brought news of the preliminary treaty, the terms of which allowed Britain to remain in possession of Gibraltar.

[138][a] Whilst after their defeat at Yorktown the British signed a Preliminary Peace in November 1782 to grant the US Congress independence, they also ceded the US its American territory to the "middle of the Mississippi River", and navigation "to the sea" that it had won in 1763 from the French.

Four British regiments engaged in the defence were granted the badge of the Castle of Gibraltar with the motto "Montis Insignia Calpe," in commemoration of the gallant part they took in the "Great Siege."

[144] Baron Münchhausen recorded in the fourth version of the book by Rudolf Eric Raspe his visit to Gibraltar, arriving on board Admiral Rodney's flagship HMS Sandwich.