A Declaration of War is a formal declaration issued by a national government indicating that a state of war exists between that nation, and one or more others.

Declarations of war and international law

In classical public international law, a declaration of war entailed the recognition between countries of a state of hostilities between these countries, and such declaration acted to regulate the conduct between the military engagements between the forces of the respective countries. In the twentieth century, the concept of war as such has been gradually replaced with the authorized use of force as recognized under international norms. The League of Nations formed in 1919 in the wake of the First World War, and the General Treaty for the Renunciation of War 1928 signed in Paris, demonstrated that world powers were seriously seeking a means to prevent the carnage of the world war. However, these powers were unable to stop the Second World War and, thus, the United Nations System was put in place after that war in an attempt to prevent international aggression through a declaration of war. Due to these developments, states that saw valid reasons for aggression against other states could take action against aggressor states that may appear similar to the classical definition of war before the twentieth century; the justification of the use of state sponsored force could be found within the ambit of these developing international law norms. In many ways the 2003 Iraq War demonstrate the limits of such an approach in international law.

History

Declarations of war have been acceptable means and diplomatic measures since the Renaissance, when the first formal declarations of war were issued.

Declarations of war have been phased out as a diplomatic tool since the end of the Second World War, particularly in the case of the United States. Among other reasons, this is because the legal concept of a "state of war" brings with it many logistical complications involving the established laws of war and other complex political issues.

Current declarations

As of 2004, a few declarations of war remain in effect, although largely ignored and retained for only political purposes.

• North and South Korea have remained legally at war since the Korean War
• Israel is still at war with Lebanon and Syria since the Yom Kippur War.
• There is some debate as to whether or not Japan is still technically at war with Russia. Although the Soviet Union declared War on Japan in 1945 and never repealed, some say that since the Soviet Union no longer exists, neither does the declaration.

United States

See Declaration of war by the United States.