Final answer:
The phrase indicates that courage and determination are more crucial to success than physical size or strength, relevant both in physical confrontations and when facing adversity.
Step-by-step explanation:
The phrase "It's not the size of the dog in the fight, it's the size of the fight in the dog" means that success is determined not by one's physical characteristics or external circumstances, but by the determination and spirit within.
For example, in a quarrel between two dogs, it's not necessarily the larger animal that will win, but the one with more courage and will to fight. Similarly, when a person is faced with adversity, their success is not strictly dependent on their resources but their willingness to persevere and face the challenges head-on.
The quote also implies that in any conflict, including one involving a large army, the key to victory lies in the determination and strategies employed rather than mere numbers or size.