The rapidly growing and modernizing Argentine military of the 1920s, whose budget had risen threefold in the decade, lacked a commensurate headquarters, and had been housed since the late 19th century in a Montserrat neighbourhood structure formerly used by the National Mint.

President Juan Perón renamed the landmark the Edificio Libertador in 1950 to honor the centennial of the death of General José de San Martín (known locally as the Liberator of Argentina, Chile and Peru).

The tunnels connecting the building to the presidential offices helped save the populist leader's life during the September 16–19, 1955, Revolución Libertadora coup against him, when he took refuge in the War Ministry before being ultimately deposed and exiled.

[5] Its importance as the effective nerve center of Argentine government during the subsequent dictatorship was later dramatized by a scene filmed in the building by director Fernando Solanas for his acclaimed 1987 drama, Sur.

[7] Following the installation of security systems, libraries, archives and a tunnel connecting the building to the Casa Rosada, as well as the lengthy and politically sensitive process of assigning wings and pavilions to the myriad Argentine military bureaus, the new War Ministry was inaugurated in April 1943.