Like Marshal Concha, marquis del Duero, he would have preferred to let events develop enough to allow of the dynasty being restored without force of arms, and he severely blamed the conduct of the generals when he first heard of the pronunciamiento of Marshal Campos at Sagunto.
He took office under Marshal Serrano during 1874, after the pronunciamiento of General Pavia had done away with the Cortes and the Federal Republic. He vainly attempted to crush the Carlists in 1874, and to check the Alphonsist military conspiracy that overthrew the government of Marshal Serrano at the end of December 1874.
At the close of the war the queen regent and her ministers attempted to elbow out Espartero and his followers, but a pronunciamiento ensued in Madrid and other large towns which culminated in the marshal's accepting the post of prime minister.
Next year, however, a revolt broke out against Bustamante, which was joined by Santa Anna, and eventually resulted in a pronunciamiento in favour of Gomez Pedraza.
O'Donnell's pronunciamiento in 1856 put an end to the Cortes, and the militia was disarmed, after a sharp struggle in the streets of the capital.