Twice he obliged the Carlists to raise the siege of Bilbao before he was appointed commander-in-chief of the northern army on the r7th of September 1836, when the tide of war seemed to be setting in favour of the pretender in the Basque provinces and Navarre, though Don Carlos had lost his ablest lieutenant, the Basque Zumalacarregui.
In 1838 Espartero carefully opened up negotiations with Maroto and the principal Carlist chiefs of the Basque provinces.
The territory occupied by the Basque Provinces forms a triangle bounded on the west and south by the provinces of Santander, Burgos and Logrono, on the east by Navarre, on the north by France and the Bay of Biscay.
Though the three Basque Provinces were thus united to the crown of Spain, they still remained a land apart (tierra apartada).
But their representatives, assisted by the senators and deputies of the Basque Provinces in the Cortes, negotiated successive pacts, each lasting several years, securing for the three Provinces their municipal and provincial self-government, and the assessment, distribution and collection of their principal taxes and octroi duties, on the understanding that an agreed sum should be paid annually to the state, subject to an increase whenever the national taxation of other provinces was augmented.
