Napoleon's strategy was to make a strong attack towards Burgos splitting off the army of Blake from the others and to outflank them by then swinging both north and south.

He decided to defend a line 17 kilometres (11 mi) long stretching west from Tudela along the Ebro, then along the Queiles River to Cascante and finally to Tarazona at the foot of the Moncayo Massif.

Castaños had insufficient men to hold a line of this length so he asked General Juan O'Neylle, who had two divisions at Caparroso on the east bank of the Ebro, for help.

O'Neylle moved promptly to the east bank of the Ebro opposite Tudela but decided not to cross the river until the next day.

By the time O'Neylle's own division was crossing it had to fight French skirmishers who were at the top of the Cabezo Malla ridge.

Although this attack was repelled it showed the weakness of the Spanish positions, especially the 5 kilometres (3 mi) gap between Castaños and La Peña's force at Cascante.

By noon on 23 November 1808 they had received orders to move: La Peña to close the gap at Tudela and Grimarest to Cascante.

Both men failed to carry out these orders other than La Peña moving two battalions and a detachment of provincial Grenadiers to Urzante.

Then the French cavalry under General of Division Charles Lefebvre-Desnouettes charged the gap between Roca and Saint-Marcq causing the collapse of the Spanish right.

La Peña and Grimarest finally united at Cascante late in the day giving them a total of 21,000 men against Lagrange's division which was 6,000 strong plus Colbert and Digeon.