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.
Malice the Webseries, a Phil Cook Eagle Films Production. MILITARY TRIBUNE. A Tribune is a Legion commander who is either of Centurion rank or Senatorial status. This is the initial rank that most Legion commanders will assume upon ascending to Rome's high command.