These military posts are here called presidios.
"A New Voyage Round the World, in the years 1823, 24, 25, and 26, Vol. 2"
Otto von Kotzebue
Still their loyalty remained unshaken; they implicitly obeyed even that command of the King which closed their ports against all foreign vessels; and as the republicans were considered as foreigners, and no ships arrived from Spain, the missions, as well as the presidios, soon began to suffer the greatest scarcity of many necessaries which the country did not produce.
"A New Voyage Round the World, in the years 1823, 24, 25, and 26, Vol. 2"
Otto von Kotzebue
Hence it was decided that if ports of call were established on the California coast, fresh meats and vegetables and pure water could be supplied to the galleons, and in addition, with presidios to defend them, they might escape the plundering pirates by whom they were beset.
"The Old Franciscan Missions Of California"
George Wharton James