The Allied troops overran the French lines behind the Bidassoa River on the coast and along the Pyrenees crest between the Bidasoa and La Rhune (Larrun).

Wellington aimed his main assault at the lower Bidasoa, while sending additional troops to attack Soult's centre.

After careful planning, Wellington launched a surprise assault which easily overran the French left flank defences.

In the Battle of San Marcial on 31 August and 1 September 1813, Soult's army was repelled in its final bid to advance into Spain.

After a costly assault followed by a brutal sack of the city, the Allies also brought the Siege of San Sebastián to a successful conclusion in early September.

[citation needed] The British commander also wanted to capture French positions that overlooked the Allied lines on the west side of the Bidassoa.

[7] Because the French troops had begun to plunder their fellow citizens, Emperor Napoleon's Minister of War, Henri Jacques Guillaume Clarke ordered Marshal Soult to defend a position as close to the frontier as possible.

Maucune held the lower Bidassoa on the Bay of Biscay, while Boyer defended the stream farther inland.

[9] Fearing an allied thrust over the Maya Pass and down the Nivelle River to the sea, Soult gave General of Division Jean-Baptiste Drouet, Comte d'Erlon 19,200 men to hold his left flank.

These troops held a line from Ainhoa to the mountain fortress of St-Jean-Pied-de-Port, covering the Maya and Roncevaux Passes.

Since cavalry was of little use in the mountains, the British commander sent most of his horse regiments to the rear, keeping a few light dragoons for patrolling.

The French never suspected that there was only 4 feet (1.2 m) of water over the lower fords at certain low tides, a fact that the Allies gleaned from Basque fishermen.

Wellington positioned five field batteries and three 18-pound siege cannon to provide fire support to the attacking infantry.

Immediately, Hay's men gained a foothold at the village of Hendaye and swung two brigades to the right to assist the crossing of Kenneth Howard's 1st Division.

Suddenly the 1/52nd (Oxfordshire) Regiment of Foot (Light Infantry) appeared out of the trees and quickly turned the tables.

He felt sympathetic to the Spanish, who had seen their nation ravaged by French soldiers, but he determined to tolerate no looting for fear of provoking a guerilla war.