A prisoner-of-war camp (often abbreviated as POW camp) is a site for the containment of enemy fighters captured by a belligerent power in time of war. There are significant differences among POW camps, internment camps, and military prisons. Purpose-built prisoner-of-war camps appeared at Norman Cross in England in 1797 during the French Revolutionary Wars and HM Prison Dartmoor, constructed during the Napoleonic Wars, and they have been in use in all the main conflicts of the last 200 years. The main camps are used for marines, sailors, soldiers, and more recently, airmen of an enemy power who have been captured by a belligerent power during or immediately after an armed conflict. Civilians, such as merchant mariners and war correspondents, have also been imprisoned in some conflicts. With the adoption of the Geneva Convention on the Prisoners of War in 1929, later superseded by the Third Geneva Convention, prisoner-of-war camps have been required to be open to inspection by authorized representatives of a neutral power. Not all belligerents have consistently applied the convention in all conflicts. Detention of prisoners of war before the development of camps Before the Peace of Westphalia, enemy fighters captured by belligerent forces were usually executed, enslaved, or held for ransom. This, coupled with the relatively small size of armies, meant there was little need for any form of camp to hold prisoners of war. The Peace of Westphalia, a series of treaties signed between May and October 1648 that ended the Thirty Years' War and the Eighty Years' War, contained a provision that all prisoners should be released without ransom. This is generally considered to mark the point where captured enemy fighters would be reasonably treated before being released at the end of the conflict or under a parole not to take up arms. The practice of paroling enemy fighters had begun thousands of years earlier, at least as early as the time of Carthage but became normal practice in Europe from 1648 onwards. The consequent increase in the number of prisoners was to lead eventually to the development of the prisoner of war camps. Development of temporary camps Following General John Burgoyne's surrender at the Battle of Saratoga in 1777, several thousand British and German (Hessian and Brunswick) troops were marched to Cambridge, Massachusetts. For various reasons, the Continental Congress desired to move them south. For this purpose, one of the congressmen offered his land