The Carlists besieged San Sebastián at the end of 1835 under the command of General Sagastibeltza. His aim was to attack and take the city, but General Egia, the chief Carlist leader, wanted to keep up the siege without attacking.
The residents appealed for help from the Liberal leader Córdoba, who sent them the British Legion Sagastibeltza asked Egia for more men, but he himself needed more troops and could not send reinforcements.
On the 5th of May, 4,500 British and 1,500 Liberals under the command of General Lacy Evans charged at the positions of the Carlists, who retreated to Lugaritz, Munto and Puio.
The Carlists of Aiete stopped the British attack with three cannons. In the meantime, those who had left the Convent del Antiguo and fortified themselves in Lugaritz had to endure the toughest Liberal attack with bayonets. Many men were lost and they were forced to stop and retreat. Two ships from the British fleet, the "Phoenix" and the "Salamander", pointed their cannons at Carlist positions and burnt the hamlet of Lugaritz. To add insult to injury, General Sagastibeltza received a shot to the head during a bayonet charge and was killed instantly.
Reinforced by 1,300 soldiers who had arrived by boat, the British launched their attack again and forced the Carlists to retreat to Oriamendi
Despite winning the battle and San Sebastián celebrating the victory, the Liberals only managed to expand the perimeter of the siege slightly. The British Legion was left with 150 dead and over 600 wounded; the Liberals calculated 100 deaths, while the Carlists ended the battle with 60 dead and 200 wounded, though the loss of Sagastibeltza was a severe blow. San Sebastián continued under siege. In March of the following year, the Battle of Oriamendi the harshest combat of all, was fought.
Two months later, taking advantage of the expedition of Don Carlos, San Sebastián managed to break the blockade after taking Hernani.