He labored, therefore, to check the increase of slave power, by the only means which, probably, appeared feasible at that time.
But a crisis in his senatorial career at length arrived.

The commerce of the United States had suffered greatly by "Orders in Council," and "Milan Decrees." Our ships were seized, conducted into foreign ports and confiscated, with their cargoes.

American seamen were impressed by British cruisers, and compelled to serve in a foreign navy.

The American frigate Philadelphia, while near the coast of the United States, on refusing to give up four men claimed to be British subjects, was fired into by the English man-of-war Leopard, and several of her crew killed and wounded.
These events caused the greatest excitement in the United States.
Petitions, memorials, remonstrances, were poured in upon Congress from every part of the Union.

Mr.Jefferson endeavored by embassies, negotiations, and the exertion of every influence in his power, to arrest these destructive proceedings, and obtain a redress of grievances.