The quote below comes from the War Powers Resolution:
The President in every possible instance shall consult with Congress before introducing United States Armed Forces into hostilities or into situation where imminent involvement in hostilities is clearly indicated by the circumstances, and after every such introduction shall consult regularly with the Congress until United States Armed Forces are no longer engaged in hostilities or have been removed from such situations.
Source: http://www.policyalmanac.org/world/archive/war_powers_resolution.shtml
How did the Vietnam War contribute to passage of this resolution?
It showed Republicans that Democrats were not committed to containment strongly enough.
It made it seem as though the president had broken the law.
It demonstrated the consequences of giving the president too much power over the military.
It made members of Congress question the need for continuing to give the military a large budget.