Answer: Defeating the greatest military power in the world.
Step-by-step explanation:
At the time, the British appeared unbeatable. They had a history of 100 years of military triumphs and their army was the best in the world. Their soldiers were fully equipped, extremely disciplined, well paid and fed. Their navy controlled the seas and they could raise funds easily. Furthermore, some of those funds were applied to get Hessian mercenaries to attack the Americans.