The emblem of Hanuman on the flag of Arjuna is another sign of victory because Hanuman cooperated with Lord Rama in the battle between Rama and Ravana, and Lord Rama emerged victorious.
Now both Rama and Hanuman were present on the chariot of Arjuna to help him.
Lord Krishna is Rama Himself, and wherever Lord Rama is, His eternal servitor Hanuman and His eternal consort Sita, the goddess of fortune, are present.
Therefore, Arjuna had no cause to fear any enemies whatsoever.
(Shrila Prabhupada, BG 1.20 Purport)
