What war led Colin Powell to conclude that an army should not enter into combat unless it had a clear objective?

Colin Powell's conclusion regarding military engagement and the necessity for a clear objective was significantly shaped by the Vietnam War. During this conflict, the United States faced numerous challenges, including unclear goals and shifting strategies, which ultimately led to prolonged engagement without achieving a decisive victory. The experiences of that war highlighted the consequences of entering into combat without specific, attainable objectives, as it resulted in significant loss of life and resources without clear justification. This realization subsequently influenced Powell's strategic thinking and his later military leadership principles, emphasizing the importance of defined aims before deploying forces into combat. The other wars listed did not demonstrate the same level of ambiguous objectives in the way that the Vietnam War did, thus reinforcing Powell's stance on military engagement.