 Complete the following phrase:  The port city was vulnerable to capture by the British by sea. Officials recruited soldiers and studied defenses for invasion from Delaware Bay, but built no forts or other installations. In March 1776 two British frigates began a blockade of the mouth of Delaware Bay; British soldiers were moving south through New Jersey from New York. In December fear of invasion caused half the population to flee the city, including the Continental Congress, which moved to Baltimore. General George Washington pushed back the British advance at the 