Article I, Section 8, Clause 11 of the U.S. Constitution, sometimes referred to as the War Powers Clause, vests in the Congress the power to declare war, in the following wording: [The Congress shall have Power ...] To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water... A number of wars have been declared under the U.S. Constitution, although there is some controversy as to the exact number; the Constitution does not specify the form of such a declaration. History and usage Five wars have been declared by Congress under their constitutional power to do so: the War of 1812, the Mexican–American War, the Spanish–American War, World WarI, and World WarII. In a message to Congress on May 11, 1846, President James K. Polk announced that the Republic of Texas was about to become a state. After Mexico threatened to invade Texas, Polk amassed federal troops around Corpus Christi. When Texas became a state, federal troops moved into an area in which the new international boundary was disputed. Mexican troops moved into the same area, and both forces clashed. The President then said that "after reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil. She has proclaimed that hostilities have commenced and that the two nations are now at war." Some in Congress wondered if that was actually so, including Abraham Lincoln, who wrote in a letter to his law partner:Let me first state what I understand to be your position. It is, that if it shall become necessary, to repel invasion, the President may, without violation of the Constitution, cross the line and invade the territory of another country; and that whether such necessity exists in any given case, the President is to be the sole judge.... But allow the President to invade a neighboring nation, whenever he shall deem it necessary to repel an invasion, and you allow him to do so, whenever he may choose to say he deems it necessary for such purpose—and allow him to make war at pleasure.... If, today, he should choose to say he thinks it necessary to invade Canada, to prevent the British from invading us, how could you stop him? You may say to him, "I see no probability of the British invading us" but he will say