The ordinary meaning of nap is to doze off during the day. The secondary meaning is to be offguard. Hence the phrase Catch them napping . Flying by the nap of the earth refers to the practice of flying low to the earth (undetected by radar) to catch the enemy by surprise (or napping).
the tribunes The Tribunes were elected representatives that protected the plebeians from mistreatment. The Tribunes attended meetings of the consuls or Senate in an attempt to bring justice to the plebeians.
Edison then protected his stolen idea with a hired band of club welding thugs who would bust up the equipment and the operators of movie cameras not paying him for use of his patent. One of the reasons that the film capital of the world is in Hollywood is because filmmakers were trying to get away from edison`s club welding thugs who chased them across the country.