Mexican Military

is watching any suspicious movement from his headquarters

There is nothing to do right now in the barracks, it's good that the three letters in Tamaulipas "CDN" are no longer there, that's good because they put up a lot of fight.

starts listening to the radio in the barracks

If he always sees a white or black truck, he stops it for inspection. If someone asks him something, he just tells them that it's from the navy. He has a board at hand to stick to the other signs.