In order to secure communication with New York and to supply the army, it was all-important that the fleet should be able to pass up the Delaware, which was strongly defended by forts, a bar, and a fleet of little vessels; and Howe detached troops to act against the forts. Washington lay a few miles to the north; he was joined by strong reinforcements, and determined to take advantage of the division of the British troops. He formed a plan for surprising and driving in their advanced posts, cutting their force in two, crushing their right wing, and then doubling the whole army back on the Schuylkill river where it would be at his mercy. He attacked at daybreak on October 4 under cover of a fog. The head of the British position was insufficiently guarded and the 40th regiment was driven back. At this critical moment its commander, Musgrave, and a party of his men stopped the enemy's advance by seizing a house which stood in their way and holding it against them until the army had time to form. His gallant conduct saved the army. The Americans fought well until, misled by the fog, one of their brigades fired on another. This threw them into disorder, which was increased by the drunkenness of some of their officers and men. Cornwallis came up from Philadelphia in hot haste and pressed upon them. They retreated with a loss of 673 killed and wounded, and 400 taken; on the British side the casualties were 551. Both in this action and in the battle on the Brandywine the Americans showed that they had learned to fight with resolution and to retreat in good order. The two engagements proved that though they might be defeated in the field, the war would not come to a speedy end, and this enlisted foreign sympathy and encouraged France to intervene on their side. For a month Howe was engaged in opening the passage of the Delaware. He sent for 4,000 men from New York. This reduction of the garrison was most unfortunate, for, as we shall see, it put an end to Clinton's attempt to co-operate with Burgoyne.[123] At last the defences of the river were destroyed, and communication was established between the army and the fleet. Washington retreated to Valley Forge, about twenty-five miles from Philadelphia, and there put his army into quarters. During the winter his troops suffered terribly from lack of clothing and provisions. By Christmas nearly 3,000 were unfit for duty because they were "barefoot or otherwise naked". They deserted in parties, a large number came to the British quarters, and scarcely a day passed without the resignation of an officer. In February, 1778, there was almost a famine in the camp, and Washington feared a general mutiny and dispersion.[124]