[6] Prim commanded the Spanish expeditionary army in Mexico in 1862, when Spain, Great Britain, and France sought forced payment from the liberal government of Benito Juárez for loans.

Prim was a sympathizer with the Mexican liberal cause, thus he refused to consent to the ambitious schemes of French emperor Napoleon III, and withdrew Spanish forces following a meeting with Manuel Doblado.

[7] Prim was a staunch supporter of the Union in the American Civil War and on his trip to the United States, where he visited New York and Philadelphia, he met with Lincoln in Washington.

On 6 November 1870 Amadeo, Duke of Aosta, was elected king of Spain, but General Prim, on leaving the chamber of the Cortes on 28 December, was shot by unknown assassins and died two days later.

[citation needed] After France had rejected the almost-elected Leopold of Hohenzollern because of their fear that Prussia might thereby become more powerful, Amadeo of Savoy was the most fitting who consented.