In 1795, the Jay Treaty went into effect, addressing many issues left unresolved after the American Revolution, and averting a renewed conflict. However, the treaty's neglect to address British impressment of sailors from American ships and ports became a major cause of complaint among those who disapproved of it. While non-British subjects were not impressed, Britain did not recognise naturalised American citizenship, and treated anyone born a British subject as still "British" — as a result, the Royal Navy impressed over 9,000 sailors who claimed to be American citizens.
During the wars with France (1793 to 1815), the Royal Navy aggressively reclaimed British deserters on board ships of other nations, both by halting and searching merchant ships, and, in many cases, by searching American port cities. Although this was illegal, Thomas Jefferson ignored it to remain on good terms with Britain as he was negotiating to obtain "the Floridas". This changed in 1805 when the British began seizing American merchantmen trading with the West Indies and condemning the ships and their cargoes as a prize and enforcing impressment on their crews. Under the Rule of 1756, in times of war, direct trade between a neutral European state and a British colony was forbidden if such trade had not existed in time of peace. The Americans had found a way around this by "landing" cargoes from Europe in the United States and issuing certificates that duty had been paid. The ship would then sail, with the cargo never having been offloaded or duty actually paid, as now bona fide commerce between neutral America and the West Indies. The British became aware of the practice during the court case involving the seizure of the Essex. The court ruled that the cargo of the Essex had never been intended for American markets so the voyage had not been broken and could thus be considered continuous. The end result was the blockade of New York Harbor by two British frigates, the Cambrian and the Leander, which provoked public demonstrations.
For the next year scores of American ships were condemned in admiralty courts and American seamen were impressed with increasing frequency until, in the early summer of 1807, when three deserters from the British frigate HMS Melampus lying in Chesapeake Bay enlisted on the American frigate USS Chesapeake. After searching the Chesapeake, the deserters, David Martin, John Strachan, and William Ware were found to be native-born Americans who had been wrongly impressed. Unfortunately the search had also found that a crew member listed, Jenkin Ratford, was a British deserter; however, he could not be found. Admiral Berkeley angrily issued an order to all commanders in the North Atlantic Squadron to search the Chesapeake if encountered on the high seas. Eight miles southeast of Cape Henry a boat from the British frigate HMS Leopard intercepted her but Commodore Barron declined to permit his crew to be mustered. The Leopard began approaching and the commander shouted a warning to which Barron replied "I don't hear what you say". The Leopard then fired two shots across the bow and almost immediately poured a broadside into the American ship and, without the Chesapeake returning fire, poured another two broadsides into it. Three crew were killed and eighteen wounded. The British boarding party not only arrested the British deserter but also the three Americans. The Chesapeake–Leopard Affair provoked an outcry for war from all parts of the country and Jefferson later wrote: "The affair of the Chesapeake put war into my hand, I had only to open it and let havoc loose". He ordered the state governors to ready their militias but the Embargo Act of 1807 he eventually passed only ordered all British armed vessels out of American waters and forbade all contact with them if they remained.
As a cause of the War of 1812, the impressment and ship seizures caused serious diplomatic tension, and helped to turn American public opinion against Britain. Impressment humiliated and dishonored the U.S. because it was unable to protect its ships and sailors.[11][12]