Answer:
police action
declaration of war
Step-by-step explanation:
The last time the U.S. Congress formally declared war on a nation was in 1942, when it declared war on Romania, Bulgaria, and Hungary. Ever since, all American military operations have been implemented without a declaration of war.
The intervention in Korea was no exception, and as Truman never asked Congress for a formal declaration, the intervention was labeled as a "police action".
This is similar to what happened in Iraq in 2003. Congress never declared war on Iraq, and the former president Bush was allowed to intervene under the lable of "authorization of military force".