Howe had a plan which made a direct attack on Washington unnecessary. He turned southward and occupied the east shore of the Hudson River. On the 16th of November took place the worst disaster which had yet befallen American arms. Fort Washington, lying just south of the Harlem, was the only point still held on Manhattan Island by the Americans. In modern war it has become clear that fortresses supposedly strong may be only traps for their defenders. Fort Washington stood on the east bank of the Hudson opposite Fort Lee, on the west bank. These forts could not fulfil the purpose for which they were intended, of stopping British ships. Washington saw that the two forts should be abandoned. But the civilians in Congress, who, it must be remembered, named the generals and had final authority in directing the war, were reluctant to accept the loss involved in abandoning the forts and gave orders that every effort should be made to hold them. Greene, on the whole Washington's best general, was in command of the two positions and was left to use his own judgment. On the 15th of November, by a sudden and rapid march across the island, Howe appeared before Fort Washington and summoned it to surrender on pain of the rigors of war, which meant putting the garrison to the sword should he have to take the place by storm. The answer was a defiance; and on the next day Howe attacked in overwhelming force. There was severe fighting. The casualties of the British were nearly five hundred, but they took the huge fort with its three thousand defenders and a great quantity of munitions of war. Howe's threat was not carried out. There was no massacre. Across the river at Fort Lee the helpless Washington watched this great disaster. He had need still to look out, for Fort Lee was itself doomed. On the nineteenth Lord Cornwallis with five thousand men crossed the river five miles above Fort Lee. General Greene barely escaped with the two thousand men in the fort, leaving behind one hundred and forty cannon, stores, tools, and even the men's blankets. On the twentieth the British flag was floating over Fort Lee and Washington's whole force was in rapid flight across New Jersey, hardly pausing until it had been ferried over the Delaware River into Pennsylvania.