Hostilities between Great Britain and some of her North American colonies began on April 19,
1775. In response, Great Britain issued a “seize and detain” order against rebel American
shipping in September 1775, and then passed the Prohibitory Act, which banned all commerce
with the rebel colonies and authorized the seizure of all American ships, effective March 1, 1776.
Warships were sent to North America to enforce this undeclared commercial blockade, and four
stages of the British blockade can be identified:
Partial Blockade: Under the “seize and detain” order, small British squadrons were sent
to important American ports and enforced a partial blockade from September 1775 to
March 1776.
First Phase of the Full Blockade: From March 1776 to June 1778, British naval forces
in North America grew rapidly, but were mainly used to support army operations. Ships
on blockade reached a peak of 32 warships.
Second Phase of the Full Blockade: The French entry into the war caused the British to
withdraw ships from North America and virtually abandon the blockade from July 1778
to October 1781. Starting in September 1778, loyalist privateers were very effective in
maintaining the blockade.
Third Phase of the Full Blockade: The end of British army actions and departure of the
French fleet allowed the Royal Navy to re-assert a close blockade from November 1781
until peace was declared in March 1783.