Which of the following was a declared war?

a. War of 1812

b. Korean War

c. Vietnam War

d. Iraq War

The War of 1812 was a declared war. The correct option among all the options given in the question is option "a". With the passage of time it is important to understand the global scenario and the implications of going on a declared full scale war. The evolving of atomic bombs makes it difficult for the United states to go on a full scale declared war as that would mean huge damage for both sides.