Armada of 1779 The Armada of 1779 was a large joint French and Spanish fleet intended , with the aid of a feint by the American Continental Navy , to facilitate an invasion of Britain , as part of the wider American War of Independence , and in application of the Franco - American alliance . The initial Franco - Spanish plan was to seize the Isle of Wight , and then capture the British naval base of Portsmouth which France planned to retain after the war . Ultimately no fleet actions were fought in the Channel and the French and Spanish invasion never materialised . The threat to Britain drew comparisons with the Spanish Armada of 1588 . Background . In 1778 , the British Royal Navy failed to secure a victory against the French Marine Royale at the Battle of Ushant , leading French naval figures to believe that they could have won if their force had been larger . On 12 April 1779 , France , which had directly allied itself with the Americans in February 1778 , signed a secret treaty with Spain , bringing it into the war against Great Britain . Fearful of the consequences in their own American empire , the Spanish did not openly support the Americans rebelling against British rule , but were willing to undertake direct operations against British interests . Spain instead sought to regain various territories , most notably the fortress of Gibraltar , which gives its holder considerable power over the entrance to the Mediterranean Sea . On 3 June 1779 the French fleet at Brest unexpectedly left port and sailed southward , then on 16 June Spain declared war on Great Britain . Gathering the forces . The plan was for the French fleet , commanded by Admiral d ' Orvilliers ( who had also led at Ushant ) , including 30 ships of the line and numerous smaller vessels , to meet a Spanish fleet off the Sisarga Islands , near Corunna in north - west Spain . When the French reached the rendezvous point , the Spanish fleet was not there , because ( the Spanish later claimed ) the winds were unsuitable , so d ' Orvilliers had to wait for them . The ships from Brest had deliberately departed before they were fully supplied , to avoid the possibility of being blockaded by the British . Serious problems consequently arose as the wait dragged out to several weeks , and no arrangements were made to take on additional supplies in Spain . Scurvy weakened the crews , and in the hot , crowded shipboard conditions , typhus and smallpox also broke out . The Spanish fleet , commanded by Don Luis de Córdova ( who was to be subordinate to d ' Orvilliers in the joint enterprise ) , including 36 ships of the line , finally arrived on 22 July . An army of over 40 , 000 men was slowly being gathered around Le Havre and St . Malo in northern France , with 400 transport boats . The purpose of the combined fleet was to put the Royal Navy out of action , so that the army could be safely transported across the English Channel ( La Manche ) , whereupon it would set up a base on the Isle of Wight or the nearby British coast . At the time there were fewer than 40 Royal Navy ships of the line available in the English Channel area , newly under the command of ailing 64 - year - old Sir Charles Hardy , who had been desk - bound for 20 years . On 25 July the Franco - Spanish armada set sail northwards to take on the British fleet , with contrary winds greatly slowing its progress . As time passed , it also became apparent that the diseases which had afflicted the French ( and killed d ' Orvilliers ' only son , a lieutenant in the fleet ) was spreading to the Spanish . Having missed opportunities to seize two important British convoys of merchant ships from the West Indies ( something they did not learn until later ) , which reached Plymouth on 31 July , the fleet finally passed Ushant on 11 August and entered the Channel . Three days later , a squadron under American colours ( though consisting mostly of French ships with French crews ) set sail from the French port of L ' Orient , heading northward towards Ireland as a diversion . This diversionary fleet was commanded by John Paul Jones , a captain with an alarming reputation in Britain . Action against the Royal Navy . What d ' Orvilliers did not know was that the British fleet was not in the Channel . Having learned that the French fleet had gone out into the Atlantic in June , Admiral Hardy was patrolling off the Scilly Isles . On 14 August , the massive combined fleet came within sight of the English coast , causing a wave of alarm which quickly spread through the country . The alarm did not spread quickly enough to reach the Royal Navy ship , which left Plymouth on 15 August to join Hardy on patrol . On 16 August the French and Spanish ships , then sailing slowly eastwards up the Channel , received orders from France to turn around , as it had been decided that the best place for the troops to land would be near Falmouth in Cornwall . D ' Orvilliers considered this a very bad idea , and sent a reply message to France asking the government to reconsider . The next day " Ardent " met an outlying French squadron of the great fleet , but was fooled into thinking it was British , and was swiftly captured . The allies hovered off Plymouth , waiting for a reply to d ' Orvilliers ' message . On 18 August a gale from the east drove them far to the west and out into the Atlantic . This had one beneficial result : as they struggled eastward again , on 25 August the allies finally learned the location of Hardy ' s fleet . They decided to neutralise it quickly , because they were finding it increasingly difficult to cope with sickness and lack of food . The allies steered for the Scilly Isles with the intention of forcing a battle , but Hardy decided to try to avoid battle . On 31 August , under cover of fog , his fleet slipped past Land ' s End and he began leading his would - be opponents as far as he could towards the key British naval base of Portsmouth . Remarkably , on 3 September , the British fleet , completely undamaged , reached the well - defended safety of the Solent , and set about equipping for battle . This was a problem for the allies , who were losing men daily to sickness . French military planners also realised that if the invasion was postponed much longer , troops would be fighting through the British autumn and winter . That day , the leaders of the great armada abandoned their campaign and set sail for Brest . Aftermath . The attempted invasion was worrying to the British , particularly as John Paul Jones ' s squadron began threatening ports on the east coast shortly after its arrival . Hasty improvements were made to coastal defences – the first earthworks were erected on the Western Heights at Dover ( though their main phase dates to the planned invasion by Napoleon soon afterwards ) and at Portsmouth Fort Gillkicker was built . For the Spanish , the expedition was an expensive waste of time . It prevented them from bringing their full force to bear on Gibraltar , which had strengthened its defences after weak early attacks , and would successfully hold out until the end of the war . For the French , the expedition was a disaster . Keeping so many ships at sea , and so many troops waiting at embarkation ports for months on end was hugely expensive — and many good sailors died of disease . D ' Orvilliers resigned his post soon after returning to France . The French and Spanish fleets continued joint operations , but more usually as a precaution for troop landings against isolated British garrisons than as a direct challenge to the Royal Navy ( notable exceptions being the unsuccessful commitment to the Great Siege of Gibraltar , and another abortive pursuit of the Channel Fleet in August 1781 , which was not connected with an invasion plan ) . The French Navy , which had been greatly improved after the Seven Years ' War , was much more successful in the war acting independently of the Spanish .