His father, Eduardo Policarpo Lonardi Monti was born in Ospitaletto (Brescia),[2] while his mother, Blanca Delia Doucet Santa Ana, was from Rosario.

Lonardi was appointed military attaché to Chile during the presidency of Ramón Castillo in 1942, shortly afterward he was declared "persona non grata" by the Chilean government on accusations of espionage.

Eduardo Lonardi, a Catholic nationalist, assumed leadership of the Revolución Libertadora junta that overthrew Juan Perón on September 16, 1955.

He was greeted by chants of Cristo Vence ("Christ is Victorious") when arriving in Buenos Aires.

Favoring a transition with "neither victors nor vanquished", his conciliatory approach was deemed too soft by the liberal faction of the armed forces, who deposed him less than two months into his de facto presidency and replaced him with hard-liner Pedro Aramburu.