Final answer:
The lack of federal power in the Articles of Confederation compromised the national defense as the government could not raise, fund, or maintain an adequate army, which led to vulnerability and contributed to the realization that the U.S. needed a stronger central government.
Step-by-step explanation:
The lack of federal power in the Articles of Confederation led to challenges with the army because the national government did not have the power to raise an army or navy, nor could it enforce discipline or adequately fund the military. Fears of a standing army had led the writers of the Articles to leave defense to the states. However, the central government's dependence on states to provide soldiers resulted in an inadequate national defense. Additionally, the government's inability to impose taxes under the Articles left it underfunded and unable to pay debts or raise money for defense, which was evident during events like Shays' Rebellion.
The lack of federal power to enforce discipline and fund the army meant that the young nation was vulnerable during a time when foreign threats persisted. The Articles of Confederation greatly limited the power of the new national government, leading to the recognition of the need for a stronger central government to handle these and other challenges, eventually resulting in the development of the U.S. Constitution.