Alfonso XII lived only 27 years and reigned for only eleven, from 1874 to 1885, when a crisis of tuberculosis that he had been secretly suffering for years ended him.

His accession to the throne put an end to the disastrous First Republic, and he became known as "the Peacemaker." After turbulent years of war and the failed monarchy of Amadeo of Savoy (1871-1873), he came to power to restore the Bourbon monarchy, which had ended when his mother Isabel II fled to France following the Glorious Revolution in 1868. Ultimately, it marked the consolidation of the monarchy after so many conflicts. Furthermore, during his reign, the Third Carlist War ended, and a transitional peace agreement was signed in Cuba.

He promoted a strictly non-democratic constitutional monarchy, with a political system based on the "peaceful rotation" of parties between conservatives and liberals (Cánovas and Sagasta). This angered other new movements (socialists, communists, anarchists), who sowed Spain with attacks and attempted to kill him twice.

The truth is that Alfonso XII promoted the modernization of Spain, seeking national unity, social peace and economic progress.

His reign was as intense as his private life, and he died without knowing whether the child his second wife was expecting would be a son and his reign would continue, or whether there would be renewed wars in Spain over the disputed throne. And it was a Verón, Alfonso XIII, the first Spanish king to be born in 1886, who was born shortly after his death.