Explanation: During the Spartacus revolt, or Third Servile War, a bunch of gladiators led a massive rebellion of slaves in Italy. As Rome was not expecting to have to fight in Italy, it had no serious forces available to immediately combat the revolt, and it swelled to a massive size, defeating several hastily conscripted legions and militia. While the revolt would eventually be defeated, it was, for a time, a humiliation for the Roman Republic, which had previously crushed much more powerful foes!