Together with many others, including his uncle Giuseppe, between 1798 and 1800 Montebello was part of the resistance of the Maltese against the French. He was stationed at Żejtun (at "Tal-Borg"), and gave his share within a team of resistance fighters. The team's job was to intercept any manoeuvring by or to the French troops blockaded in Valletta through the road leading to Cottonera from the east, and to organise and manage supplies around that area. Despite some skirmishes―which had even left some casualties on both sides―Montebello's involvement does not seem to have been military, as some suggested, but rather of a logistical nature. In fact, together with two others (Luigi Agius, a doctor of canon and civil law, and Vincenzo Borg, later a Companion of the Order of St. Michael and St. George) Montebello served as "consultore legale" (legal adviser) under the command of Giuseppe Abela. The team's General Headquarters was situated at San Giuseppe (Hamrun), under the general command of Francesco Saverio Caruana. Caruana was a Monsignor who had studied philosophy under Michael Xerri. He was professor of philosophy and mathematics at the bishop’s seminary at Mdina, and later appointed Bishop of Malta (1831–47).