Once Washington retreated to Pennsylvania, New England militias had to fortify the Hudson Highlands, a choke point on the river north of Haverstraw Bay. As a result, the Continentals started building Fort Clinton on the other side of the river from Fort Montgomery. In the year 1777, Washington expected General Howe to sail his army north to Saratoga in order to meet up with General Burgoyne. This would result in the Hudson River being sealed off. However, Howe surprised Washington by sailing his army south to Philadelphia, conquering the Patriot capital. Washington was out of position and sought to defend Philadelphia, but to no avail. Meanwhile, Howe left Sir Henry Clinton in charge of a smaller force to be docked in New York City, with the permission to strike the Hudson Valley at any time. On October 5, 1777, Clinton's army did so. At the Battle of the Hudson Highlands, Clinton's force sailed up the Hudson River and attacked the twin forts. Along the way, the army looted and pillaged the village of Peeksill. The Continentals fought hard at the battle, but they were badly outnumbered and were fighting in unfinished forts. Washington's men were caught between defending Philadelphia and defending the Hudson Valley. In the end, the British took the fort, as well as taking Philadelphia around the same time. However, Clinton and his men returned to New York City soon afterward.