But while the garrison of Philadelphia limited its excursions to plundering farms and the country adjacent for wood, forage and provisions generally, both commanding generals were studying the relations of the Delaware River to the conduct of all future operations upon any decisive scale. The river had been so obstructed that the fleet of Admiral Howe, which had been compelled to land his army at the head of the Chesapeake in September, could not yet communicate with the army since it gained the city. He arrived off Newcastle on the sixth day of October. Washington realized that by retaining control of the Delaware he not only restricted the supply of provisions and military stores to the garrison, but retained easy communications with New Jersey and the Camps of Instruction and rendezvous at the adequately fortified posts of Morristown and Middlebrook. At Billingsport, _chevaux-de-frise_ obstructed the channel. Just below the mouth of the Schuylkill was Fort Mifflin, on Mud Island. On the opposite shore, at Red Bank, was Fort Mercer. Washington determined to maintain these posts, or make their acquisition by the enemy most costly in men and materials. His foresight grasped, as if in hand, the rapidly maturing facts, that Britain could not much longer meet the drain of the American war and at the same time hold her own against her European foes; and that America needed only a thoroughly concerted effort to consummate her independence. Colonel Christopher Green, courageous at Bunker Hill and during Arnold’s expedition to Canada, was assigned to command Fort Mercer, with troops from his own State, Rhode Island. Lieutenant-Colonel Smith, of Maryland, with Maryland troops, was stationed at Fort Mifflin. These little garrisons were strengthened by the detail of four hundred Continental troops to each. In these details, the same wisdom marked Washington’s choice; as Angel’s Rhode Island regiment reported to Greene, and a portion of Greene’s Virginia regiment reported to Smith.