A new army had been enlisted in the trenches before Boston to take the place of that first one, whose term of service expired with the new year, 1776. On paper it consisted of twenty-eight battalions, with an aggregate of 20,372 officers and men. By the actual returns, made up shortly before the army marched for New York, there were 13,145 men of all arms then enrolled, of whom not more than 9,500 were reported as fit for duty. These were all Continentals,[2] as the regular troops were then called, to distinguish them from the militia. [Sidenote: It marches to New York.] Immediately upon the evacuation of Boston by the British (March 17, 1776), the army marched by divisions to New York, the last brigade, with the commander-in-chief, leaving Cambridge on April 4.[3] This move distinctly foreshadows the general opinion that the seat of war was about to be transferred to New York and its environs. There is no need to discuss the general proposition, so quickly accepted by both belligerents, as regards the strategic value of New York for combined operations by land and sea. Hence the Americans were naturally unwilling to abandon it to the enemy. A successful defence was really beyond their abilities, however, against such a powerful fleet as was now coming to attack them, because this fleet could not be prevented from forcing its way into the upper bay without strong fortifications at the Narrows to stop it, and these the Americans did not have. Once in possession of the navigable waters, the enemy could cut off communication in every direction, as well as choose his own point of attack. Afraid, however, of the moral effect of giving up the city without a struggle, the Americans were led into the fatal error of squandering their resources upon a defence which could end only in one way, instead of holding the royal army besieged, as had been so successfully done at Boston. Having arrived at New York, Washington's force was increased by the two or three thousand men who had been hastily summoned for its defence,[4] and who were then busily employed in throwing up works at various points, under the direction of the engineers. [Sidenote: Make-up of the army.]