Title: Declaration of war
Content:  In the United States, Congress, which makes the rules for the military, has the power under the constitution to "declare war". However neither the U.S. Constitution nor any Act of Congress stipulate what format a declaration of war must take. War declarations have the force of law and are intended to be executed by the President as "commander in chief" of the armed forces. The last time Congress passed joint resolutions saying that a "state of war" existed was on June 5, 1942, when the U.S. declared war on Bulgaria, Hungary, and Romania. Since then, the US has used the term "authorization to use military force," as in the 
Title: Declaration of war by the United States
Content:  such a war." in effect saying an authorization suffices for declaration and what some may view as a formal congressional "Declaration of War" was not required by the Constitution. The last time the United States formally declared war, using specific terminology, on any nation was in 1942, when war was declared against Axis-allied Hungary, Bulgaria, and Romania, because President Franklin Roosevelt thought it was improper to engage in hostilities against a country without a formal declaration of war. Since then, every American president has used military force without a declaration of war. This article will use the term "formal declaration of war" to mean congressional legislation that uses the phrase "declaration of war" in the title. Elsewhere, this article will use the terms "authorized by Congress," "funded by Congress" or "undeclared war" to describe other such conflicts.
Title: Declaration of war by the United States
Content:  The United States has formally declared war against foreign nations in five separate wars, each upon prior request by the President of the United States. Four of those five declarations came after hostilities had begun. James Madison reported that in the Federal Convention of 1787, the phrase "make war" was changed to "declare war" in order to leave to the Executive the power to repel sudden attacks but not to commence war without the explicit approval of Congress. Debate continues as to the legal extent of the President's authority in this regard. Public opposition to American involvement in foreign wars, particularly during the 1930s, 
Title: Powers of the United States Congress
Content:  have initiated war without congressional war declarations; Truman called the Korean War a "police action" and the Vietnam War lasted over a decade without a declaration of war. In 1970, Time magazine noted: "All told, it has been calculated, U.S. presidents have ordered troops into position or action without a formal congressional declaration a total of 149 times" before 1970. In 1993, one writer noted "Congress's war power has become the most flagrantly disregarded provision in the Constitution," and that the "real erosion (of congressional authority to declare war) began after World War II." President George H. W. Bush claimed 
Title: Declaration of war by the United States
Content:  A declaration of war is a formal declaration issued by a national government indicating that a state of war exists between that nation and another. A document by the Federation of American Scientists gives an extensive listing and summary of statutes which are automatically engaged upon the United States declaring war. For the United States, Article One, Section Eight of the Constitution says "Congress shall have power to ... declare War." However, that passage provides no specific format for what form legislation must have in order to be considered a "declaration of war" nor does the Constitution itself use this term. In the courts, the United States Court of Appeals for the First Circuit, in Doe v. Bush, said: "[T]he text of the October Resolution itself spells out justifications for a war and frames itself as an 'authorization' 
Title: Undeclared war
Content:  There is no specific format required under United States law for the way an official war declaration will be structured or delivered. The United States Constitution states: "The Congress shall have Power […] To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water". As of August 2013, the United States Congress has formally declared war 13 times, and has not done so since 1942. The United States did not declare war during its involvement in Vietnam, although the Gulf of Tonkin Resolution authorized the escalation and use of military force in the Vietnam War without a formal declaration of war. On at least 125 occasions a US president has employed military forces without authorization from Congress. One of the most significant of these occasions was the Korean War, a conflict that resulted in over 142,000 American casualties (about 40,000 deaths and over 100,000 injuries).
Title: United States Congress
Content:  for the military. Some critics charge that the executive branch has usurped Congress's constitutionally defined task of declaring war. While historically presidents initiated the process for going to war, they asked for and received formal war declarations from Congress for the War of 1812, the Mexican–American War, the Spanish–American War, World War I, and World War II, although President Theodore Roosevelt's military move into Panama in 1903 did not get Congressional approval. In the early days after the North Korean invasion of 1950, President Truman described the American response as a "police action". According to Time magazine in 1970, "U.S. presidents [had] ordered troops into position or 
Title: War of 1812
Content:  while it was not a formal declaration of war. This was the first time that the United States had declared war on another nation and the Congressional vote was the closest vote in American history to formally declare war. None of the 39 Federalists in Congress voted in favour of the war, while other critics referred to it as "Mr. Madison's War". Just days after war had been declared, a small number of Federalists in Baltimore were attacked for printing anti-war views in a newspaper, which eventually led to over a month of deadly rioting in the city. Prime Minister Spencer Perceval was assassinated in London on 11 May and Lord Liverpool came to 
Title: Origins of the War of 1812
Content:  In the US House of Representatives, a group of young Democratic-Republicans, known as the "War Hawks," came to the forefront in 1811 and were led by Speaker Henry Clay of Kentucky and by John C. Calhoun of South Carolina. They advocated going to war against Britain for all of the reasons listed above but concentrated on their grievances more than on territorial expansion. On 1 June 1812, President James Madison gave a speech to the US Congress that recounted American grievances against Britain but did not specifically call for a declaration of war. After Madison's speech, the House of Representatives quickly voted (79 to 49) to declare war, and the Senate did the same by 19 to 13. The conflict formally began on 18 June 1812, when Madison signed the measure into law. It was the first time that the US had declared war on another nation, and the congressional vote was the closest-ever vote to declare war in American history. None of the 39 Federalists in Congress voted for the war, whose critics later referred to it as "Mr. Madison's War."
Title: War of 1812
Content:  On 1 June 1812, President James Madison sent a message to Congress recounting American grievances against Great Britain, though not specifically calling for a declaration of war. The House of Representatives then deliberated for four days behind closed doors before voting 79 to 49 (61%) in favour of the first declaration of war. The Senate concurred in the declaration by a 19 to 13 (59%) vote in favour. The declaration focused mostly on maritime issues, especially involving British blockades, with two thirds of the indictment devoted to such impositions, initiated by Britain's Orders in Council.{{efn|Hickey|1989}p=44}} The conflict began formally on 18 June 1812, when Madison signed the measure into law. He proclaimed it the next 

Question: when does congress declare war for the first time?
Answer: June 18, 1812.
War of 1812.