The essential feature of the third period, comprising the years 1776 and 1777, was the struggle for the state of New York and the great natural strategic line of the Mohawk and Hudson rivers. Independence having been declared, the United States and Great Britain were now fighting each other single-handed, like two separate and foreign powers. It was the object of Great Britain to conquer the United States, and accordingly she struck at the commercial and military centre of the confederation. If she could have thoroughly conquered the state of New York and secured the line of the Hudson, she would have broken the confederation in two, and might perhaps have proceeded to overcome its different parts in detail. Hence in this period of the war everything centres about New York, such an outlying expedition as that of Howe against Philadelphia having no decisive military value except in its bearings upon the issue of the great central conflict. The strategy of the Americans was mainly defensive, though with regard to certain operations they assumed the offensive with brilliant success. The period began with the disasters of Long Island and Fort Washington; it ended with the triumph of Saratoga. As the net result of the two years' work, the British had taken and held the cities of New York and Philadelphia and the town of Newport. The fortress of Ticonderoga, which they had likewise taken, they abandoned after the overthrow of Burgoyne; and in like manner they retired from the highlands of the Hudson, which the Americans now proceeded to occupy with a stronger force than before. In short, while the British had lost an army, they had conquered nothing but the ground on which they were actually encamped. Their attempt to break through the centre of the American position had ended in a total defeat, and it now began to seem clear to discerning minds that there was small chance of their being able to conquer the United States.