Final answer:
The American colonial forces became a professional and competent fighting force during the American Revolution, primarily through the formation and development of the Continental Army and the training provided by individuals like Baron von Steuben.
Step-by-step explanation:
The American colonial forces became a professional and competent fighting force during the American Revolution, particularly through the creation and development of the Continental Army. The Second Continental Congress, held in May 1775, approved the formation of a professional Continental Army with George Washington as the commander in chief. Although the army initially consisted of militias, it gradually evolved into a more disciplined and organized force over the course of the war. This transformation was facilitated by the assistance of individuals like Baron von Steuben, a Prussian military officer, who helped train and shape the Continental Army into a professional fighting force.