During the Second World War, he was appointed mayor of Cavite City by the Japanese occupation authorities but provided discreet logistical support to the guerrilla movement before resigning from office in 1944.

[2] In 1949, Montano won a seat in the Philippine Senate and authored the resolution creating the Blue Ribbon Committee, tasked with investigating graft and corruption.

[1] During this time, Montano was implicated in political violence in Cavite, particularly involving his feud with governor Dominador Camerino.

In the 1960s, Montano was also accused of involvement in smuggling imported cigarettes and other goods in Cavite, for which he later feuded with Ferdinand Marcos, Floro Crisologo and other Ilocano politicians and members of the tobacco lobby.

[2] Montano's political career ended when Congress was abolished by President Marcos after the declaration of martial law in 1972.

Montano, who was in the United States at the time, stayed in exile until Marcos' overthrow in 1986, and withdrew from politics even after his return to the Philippines.