Congress, as we have seen, enjoys by virtue of the War Clause, the sole and exclusive authority to initiate military hostilities on behalf of the American people. At its discretion, Congress may institute a state of war by choosing to either formally “declare” war on enemies of the United States, or by authorizing hostilities through passage of a joint resolution. There are also two kinds of war, which American courts have called “perfect,” or general, and “imperfect,” or limited, wars. In 1782 the Federal Court of Appeals, the prize court established by the Continental Congress, explained the difference. It stated: “The writers upon the law of nations, speaking of different kinds of war, distinguish them into perfect and imperfect: A perfect war is that which destroys the national peace and tranquility, and lays the foundation of every act of hostility. The imperfect war is that which does not entirely destroy the public tranquility, but interrupts it only in some particulars, as in the case of reprisals.” At all events, the President has no constitutional authority to initiate war or lesser military hostilities, but that has not proven to be an impediment to executive war making. Indeed, presidential aggrandizement of the war power has become a common theme for the past 60 years.
It is baffling that scholars, commentators and politicians have so often said of American history that a declaration of solemn war, fully invoking international law, has been issued on only five occasions. In fact, Congress has passed resolutions declaring general war, declarations pure and simple, on 11 occasions. On June 18, 1812, Congress by joint resolution declared that a state of war existed with Great Britain; on May 13, 1846, with Mexico; on April 25, 1898, with Spain; on April 6, 1917, with Germany; on December 7, 1917, with Austria-Hungary; on December 8, 1941, with Japan; on December 11, 1941, with Germany; on the same day with Italy; on June 5, 1942, with Bulgaria; on the same day with Hungary and with Rumania. All of these resolutions authorized the President to use the army, navy and the militia for the prosecution of the war.
In addition, Congress has passed four conditional declarations of war. These are congressional “ultimatums,” instances in which Congress asserts demands and directs the President to act, if they are not met. Two episodes are illustrative. In 1853, an American naval vessel was on the Paraguayan side of waters allegedly common to Paraguay and Argentina. Paraguay had closed its waters to foreign ships of war, and a Paraguayan fort shelled the Water Witch, which returned fire. In his annual message to Congress on December 8, 1857, President James Buchanan announced his intention to demand redress and asked Congress to authorize him to use “other means in the event of a refusal.” By joint resolution of June 2, 1858, he was authorized to “adopt such measures and use such force as, in his judgment, may be necessary and advisable.” Several ships of war were sent and the difficulties with Paraguay were adjusted by commissioners, without resorting to violence.
A second, illustrative episode, occurred during the administration of President William McKinley. On April 20, 1898, President McKinley signed a joint resolution demanding that Spain withdraw from Cuba and relinquish her authority over the island. Congress directed McKinley to use the land and naval forces to implement the resolution. On April 21, Spain severed diplomatic relations with the United States. On April 25, Congress passed an act declaring that a state of war with Spain had existed since April 21.
On several occasions, Congress has authorized limited war, that is, action restricted as to objective or as to instrument. As we shall see, the Supreme Court has held that the exercise of authority to determine the size , scope and direction of war, is part and parcel of the congressional war power, described by James Madison as authority to “commence, conclude and continue war.” These acts, harking back to the earliest days of the republic, reveal presidential deference to Congress.