The Carlists proclaimed the restoration of Catalan, Valencian and Aragonese fueros (charters) which had been abolished at the beginning of the 18th century by King Philip V in his unilateral Nueva Planta decrees.

The bell rings to the dead across the heroic town of Igualada...Horrible details...People [killed] by bayonets, burned houses, factories attacked at dawn, robberies, rap[es], insults...About the Carlists' entrance on Vendrell thousands atrocities are told, done by the followers of absolutism...

"[citation needed] In the deeply religious and conservative atmosphere of 19th century Spain, Carlism attracted a large number of followers, particularly among sections of society which resented the growing liberalism of the Spanish state.

Reforms included the confiscation and sale of church lands and other institutions that supported the old regime, the establishment of elected parliaments, the construction of railways and the general expansion of industry throughout Spain.

The resulting success allowed Carlists to gain control of the countryside, although cities like Bilbao, San Sebastián, Pamplona and Vitoria-Gasteiz stayed in Liberal hands.

On the Liberal side, Baldomero Espartero rose to prominence and replaced Maria Cristina as regent in 1840, although his subsequent unpopularity meant that he was later overthrown by a coalition of politicians and moderate military figures.

Institutions specific to certain territories, such as the fueros of the Basque Country, were removed by the liberal 1812 Constitution proclaimed in Cádiz, but were largely restored on the installation of Ferdinand VII of Spain to the Spanish throne in 1814.

Finally, the constant political unrest during the reign of Isabel II, caused by numerous changes in government and the discontent of army officers sent to fight the unsuccessful Hispano-Moroccan War, convinced many traditionalists to favor an armed uprising to restore their lost privileges.

Successive Spanish governments during La Gloriosa attempted to combat financial woes by making new loan requests to pay back existing debt, accepting ever-higher interest rates.

The Spanish government took emergency measures aimed at collecting the funds necessary for their campaign against the Carlist outbreak in the north, some of which broke the boundaries of what could be ethical and economically viable.

These war parties would carry out irregular warfare, focusing on guerrilla or partisan activities, attacking telegram posts, railways, outposts using hit and run tactics.

Regardless, the suppression of Carlist guerrillas was a hazardous and costly task that required enormous amounts of manpower and resources that, in the first stages of the war, the Liberals were unable to provide.

Several raiding parties carried out guerrilla activities across Catalonia (under the command of generals Tristany, Savalls and Castells), Castile, Galicia, Aragon, Navarre, Gipuzkoa,...

However, a quick counterattack of 1,000 government troops led by General Moriones assaulted the Carlist camp in Orokieta during the night of May 4, forcing Carlos VII to retreat to France.

In February, after the abdication of King Amadeo I and the proclamation of the First Spanish Republic, General Dorregaray arrived to lead the Carlist army in the Basque Country, starting a campaign against government forces.

At May 5, Carlist forces under the command of Dorregaray and Rada won an important victory at Eraul (Navarre), inflicting heavy casualties on a government army led by General Navarro, taking many prisoners.

Combined, the battles of Mañeru and Montejurra led to the victory of Belabieta near Villabona in Gipuzkoa, reaffirming the Carlist cause in the surrounding areas, and strengthening their army and morale.

The siege of Bilbao would last from February 21, 1874, until May 2, 1874, and was the turning point of the Third Carlist war in the Basque Provinces and Navarre, with brutal fighting between both sides for possession of the city.

Carlist besiegers, led by Joaquin Elio and Carlos VII himself, numbered around 12,000 men, and faced 1,200 government forces in addition to citizens of Bilbao recruited to serve as auxiliaries.

Carlist besiegers under the command of Nicolas Ollo, entrenched near the town of Somorrostro, repelled the attackers and inflicted heavy casualties; 1,200 government troops were killed, and many more were wounded.

Immediately, Catalan Carlists set their capital at Olot, forming a new government in San Joan de les Abadeses with Rafael Tristany as head of state.

The pronounciamiento of General Arsenio Martinez de Campos and Brigadier Daban proclaimed the restoration of the monarchy on December 29, 1874, enthroning Alfonso XII, the son of the deposed Queen Regnant Isabel II, as King.

Having lost the war in Catalonia, and faced with the advance of the two government armies led by Generals Martinez Campos and Quesada, Carlists began to prepare their last stand in the Basque Provinces and Navarre.

Government forces, under General Fernando Primo de Rivera, advanced with the intention to capture Estella in February 1876 in a final offensive to put an end to the Carlist uprising.

In response, an official Spanish decree was approved on July 21, 1876, by Prime Minister Antonio Canovas del Castillo, which abolished the Basque institutional system of Biscay, Álava, and Gipuzkoa.

Rather, the newly established Provincial Councils would be responsible for tax collection in their province as they saw fit, and would then remit a portion of the revenues, as decided by the State Treasury, to the central government.

As a result of the industrialization, Basque identity was plunged into crisis due to the perception that local customs and language were being eroded by the massive wave of immigration from diverse parts of Spain.

In December 1874, in the midst of the war, Major Martinez Campos proclaimed Alfonso XII as King of Spain through a successful military uprising, ending the First Spanish Republic.

There, before the military uprising of 1874, Alfonso XII proclaimed a manifesto, written by Canovas, which advocated monarchy as the only way to end the crisis of the revolutionary period, and which set out the most important ideas of a new Spanish political system.

The writer Benito Pérez Galdós also mentions some tales of the Third Carlist War in his books Episodios Nacionales (1872–1912), often showing them as religious bandits and mocking their leaders, who are often referred to as "wild beasts."