Assault on Cadiz ( 1797 ) The Assault on Cadiz was a part of a protracted naval blockade of the Spanish port of Cadiz by the Royal Navy , which comprised the siege and the shelling of the city as well as an amphibious assault on the port itself from June to July 1797 . After the battle of Cape Saint Vincent the British fleet led by Lord Jervis and Sir Horatio Nelson had appeared in the Gulf of Cadiz . During the first days of June the city was bombarded , but causing slight damage to the Spanish batteries , navy and city . Nelson ' s objective was to force the Spanish admiral Jose Mazarredo to leave the harbour with the Spanish fleet . Mazarredo prepared an intelligent response and the Spaniards began to build gunboats and small ships to protect the entrance of the harbour from the British . By the first days of July , after a series of failed attacks led by Rear - Admiral Nelson , and with the British ships taking huge fire from the Spanish forts and batteries , the British withdraw and the siege was lifted . The naval blockade , however , lasted until 1802 . Background . In February 1797 the British routed a Spanish fleet near Cape St . Vincent but failed to strike a solid blow against the Spanish Navy in the uneven struggle . Admiral Sir John Jervis sailed for Lisbon after the engagement , frustrated at the escape of several valuable prizes including the " Santísima Trinidad " . New orders from the Admiralty demanded him to blockade and subdue the Spanish port of Cádiz , where much of the battered Spanish squadron had sought shelter . The First Sea Lord thought that the ease of Jervis ' victory over José de Córdoba y Ramos guaranteed a successful attack on that strategic harbour . Events proved otherwise . Blockade begins . The blockade of Cadiz , which had been begun by Sir John Jervis in 1797 , had no intermission from that time until the peace of Amiens , and on the renewal of the war it was recommenced with all its former rigour . The fleet was distant from the town about 15 miles ; the Spanish fleet within the harbour , and the British in - shore squadron under the command of Rear - admiral Thomas Louis , closely watching their movements , and reporting every indication of their disposition to come to sea . and were at the mouth of the harbour , for the purpose of intercepting any supply of provisions for the enemy . Nelson said he knew no more certain means of bringing them out than starvation . Having completed these arrangements , the admiral retired with the body of the fleet to the neighbourhood of Cape St . Mary ' s between 50 and 60 miles west of Cadiz , establishing a line of communication between himself and his advanced squadron , by means of three or four intermediate ships . By keeping at this distance from Cadiz , Nelson prevented the enemy from acquiring any accurate knowledge of his force . Battle . Nelson was appointed to the command of the inner squadron blockading Cadiz . An order from Sir John Jervis directed the launches and barges of two divisions of the fleet to assemble on board , between 9 and 10 o ' clock every night , armed with carronade s , spikes , cutlasses , broad axes , and chopping knives , a lamp in each boat with spikes , a sledge - hammer , and a coil of small rope , to tow off any armed brig , mortar or gun - boat , that should be carrier , and to follow the directions of Nelson for the night . The Spaniards had equipped a number of gun - boats and large launches , in which they rowed guard during the night , to prevent the near approach of the blockaders . On these a vigorous attack was made in the night of 3 July by the British boats , headed by Nelson himself , which pursued the Spaniards close to the walls of Cadiz , and took two mortar - boats and an armed launch . In this conflict it was the admiral ' s fortune to encounter the barge of Don Miguel Tregoyen , the commander of the Spanish gun - boats . The struggle that ensued was one of the most perilous in which Nelson had ever been engaged . He fought hand to hand with the Spanish commandant , and it was his own opinion that he must have lost his life but for the devoted attachment of his faithful coxswain , John Sykes . The Spanish garrison of Cadiz at this time consisted of more than 4000 men . On the line wall facing the bay were mounted 70 pieces of cannon and eight mortars ; near the Alameda were four other mortars ; and from the Capuchins , at the back of the city , to the land point were three batteries of four guns each . Such was the strength of the place when Nelson was ordered to bombard it . The first attempt proved ineffective , as the large mortar had been materially damaged in earlier service . The second produced considerable effect in the town and among the shipping , as ten sail of the line , among them the ships carrying the flags of admirals Mazarredo and Gravina , warped out of the range of the shells with much precipitation on the following morning . On the night of 8 July , Nelson meditated another operation under his own immediate direction ; but the wind blew so strong down the bay , that it was found impossible to bring up the bomb vessel s to the point of attack in time . On the following day , he informed Earl St . Vincent that , though he hoped enough had been done to force out the Spanish fleet , yet in case there had not , he would try them again . The continuation of the blockade for most of the following three years , greatly curtailed the operations of the Spanish fleet from Cadiz until the Peace of Amiens in 1802 , allowing the Royal navy to establish its dominance in the Mediterranean . Aftermath . Nelson had some time before he proposed to the commander - in - chief an expedition against the town of Santa Cruz , in the island of Tenerife . Lord Jervis allowed Sir Horatio to select such ships and officers as he thought proper for this service . The expedition resulted in another defeat for him . The Spanish citizens of Cadiz composed a song of the victory that became very popular in Spain during the 19th century : " ¿ De qué sirve a los ingleses " . < br > " tener fragatas ligeras " < br > " si saben que Mazarredo " < br > " tiene lanchas cañoneras ? "