As Soult approached the city of Oporto his original force of 23,000 had been thinned to 16,000 troops. Casualties, relatively speaking were light, but to keep his supply and line of communication with Ney in Galicia detachments were placed in the major cities and towns along the way; these were Vigo, Tuy, Orense, Chaves and Braga. The uprising in Galicia threatened the first three locations and the Ordenanza in northern Portugal threatened the last two. Unknown to Soult, Silveira was successful in retaking Chaves as French neared Oporto.
A key link in the chain was the port of Vigo as it offered the British a toehold in the north to supply the insurgents there. On the 15th of February, Soult left a garrison of 700 men to secure the fortress and the harbour area before moving on to Orense and the frontier. By the 7th of March, the local populace rose in arms which drew the attention of both La Romana and the Central Junta in Seville and to support their effort officers were sent to help with the blockade the harbour and town of Vigo.
The French, commanded by Colonel Chalot could not prevent the insurgents from securing parts of the town and therefore remained determined to hold the fortress; not willing to surrender to a force of peasants. On the 23rd of March, two English frigates (Lively and Venus) entered the harbour and began to supply the insurgents with munitions and heavy naval guns for their use. After four days, one of the gates succumbed to the bombardment forcing Colonel Chalot to negotiate surrender.
Locating maps of Vigo during the Peninsular War is very difficult, however, you will have some success by searching for the Battle of Vigo Bay (Spanish Succession). This did produce a fine map of the harbour, city and Castro Citadel. The citadel does command the entrance to the bay but its location limits any effective control over the city.
Colonel Chalot had at his disposal 700 men which were later augmented by the paymaster-general and his escort guarding the military chest, brought the total number of defenders to 1,300. On hearing of the siege of Vigo, a relief column was sent to aid the garrison only to arrive a day late.
The insurgents, commanded by Lieutenant Morillo, are described as sufficient in number to make French defence of the entire city impossible. Some sources quote more than 3,000.
The two captains of the Lively (38) and Venus (36) had received discretionary latitude in cooperating with insurgency forces and so muskets, powder and other stores. Heavy naval guns and their crews were also brought ashore.
This is an interesting scenario if done from its entirety; from insurrection to surrender. The insurgent forces would increase with each week (7th – 13th) with the guerrilla leaders making assaults on the citadel. The French might recapture the town but as each week passes (14th – 20th) the increase numbers would make this impossible. Messengers were sent to the garrison at Tuy when the enemy grew in number. By the third week, Spanish officers will have arrived to coordinate the siege and the British Navy made their appearance to supply the Spanish with guns, powder, and naval guns. A French relief column was sent and this could arrive earlier than it did, but sources give its strength at a weak battalion (300).
I highly recommend reading PhD. B. Toy’s ‘Littoral Operations in Galicia, 1809 and how effective the British Navy helped the uprising in Galicia.
Historias de Vigo
Littoral Operations in Galicia, 1809, by Brian M. Toy, PhD, West Point
A History of the Peninsular War, C. Oman, volume II,