Regency
When Ferdinand died on 29 September 1833, Maria Christina became regent for their daughter Isabella. Isabella's claim to the throne was disputed by her uncle, the Infante Carlos, Count of Molina, who claimed that his brother Ferdinand had unlawfully changed the succession law to permit females to inherit the crown (see Carlism). Some supporters of Don Carlos went so far as to claim that Ferdinand had actually bequeathed the crown to his brother but that Maria Christina had suppressed that fact. It was further alleged that the Queen had signed her dead husband's name to a decree recognizing Isabella as heir.
Carlos' attempt to seize power resulted in the Carlist Wars. Despite considerable support for Carlos from the Roman Catholic Church and conservative elements in Spain, Maria Christina successfully retained the throne for her daughter. The Carlist Wars grew from a dispute about the succession into a dispute over the future of Spain. The supporters of Maria Christina and her daughter favored a liberal constitution and progressive social policies. In contrast, Carlos' supporters (called Carlists) favored a return to traditional society and an absolute monarchy. Ultimately, the army's loyalty to Isabella II proved the decisive issue in the war.
Read more about this topic: Maria Christina Of The Two Sicilies