Before the United States had a Navy, armed civilian privateers rather than a national fleet carried much of the Revolution's war at sea. The episode opens the two-century story of the "Fourth Arm of National Defense" with the 1776 letters of marque and a private fleet that vastly outnumbered the tiny Continental Navy.
Privateer counts vary widely, from the National Park Service's conservative figures to higher estimates of 2,000-plus vessels. Historians disagree on how decisive privateering was, and the Roosevelt attribution of "Fourth Arm" cannot be pinned to a clean quotation.



