The circumstances which led to the arrest of the spy were as follows :

Major John Andre had been long negotiating with the American general, Arnold, to put the British general, Clinton, in possession of West Point. " This post," says Major General Greene, (who, it must be remembered, was president of the court that tried Andre,) " is a beautiful little place lying on the west bank of the Hudson, a little below where it breaks through the chain of mountains called the highlands. Its form is nearly circular, in half of its circumference defended by a precipice of great height, rising abruptly from the river, and on the other by a chain of rugged, inaccessible mountains. It is accessible by one pass only from the river, and that is narrow and easily defended ; while on the land side it can be approached only at two points -- by roads that wind through the mountains and enter it at the river bank on the north and south. Great importance had always been attached to this post by the Americans, and great labor and expense bestowed upon fortifying it. It has been well called the " Gibraltar of America." The North river had long been the great vein that supplied life to the American army, and had the enemy obtained possession of this post, besides the actual loss in men and stores, the American army would have been cut off from their principal resources in the ensuing winter, or been obliged to fall back above the Highlands, and leave all the country below open to conquest, while the communication between the eastern and western States would have been seriously interrupted if not wholly excluded. Arnold therefore well knew the bearing of this post upon all the operations of the American army; and afterwards avowed his confident expectation, that had the enemy got possession of it, the contest must have ceased, and America been subdued.