DECLARATION OF WAR. An act of the national legislature, in which a state of 
war is declared to exist between the United States and some other nation. 
     2. This power is vested in congress by the constitution, art. 1, s. 8. 
There is no form or ceremony necessary, except the passage of the act. A 
manifesto, stating the causes of the war, is usually published, but war 
exists as soon as the act takes effect. It was formerly usual to precede 
hostilities by a public declaration communicated to the enemy, and to send a 
herald to demand satisfaction. Potter, Antiquities of Greece, b. 3, c. 7; 
Dig. 49, 15, 24. But that is not the practice of modern times. In some 
countries, as England, the, power of declaring war is vested in the king, 
but he has no power to raise men or money to carry it on, which renders the 
right almost nugatory. 
     4. The public proclamation of the government of a state, by which it 
declares itself to be at war with a foreign power, which is named, and which 
forbids all and every one to aid or assist the common enemy, is also called 
a declaration of war.