As president, Jefferson pursued the nation's shipping and trade interests against Barbary pirates and aggressive British trade policies. Starting in 1803, Jefferson promoted a western expansionist policy, organizing the Louisiana Purchase, doubling the nation's land area. To make room for white settlement, Jefferson began a controversial process of Indian tribal removal from the newly acquired territory. As a result of peace negotiations with France, his administration reduced military forces. Jefferson was reelected in 1804. His second term was beset with difficulties at home, including the trial of former vice president Aaron Burr. In 1807, American foreign trade was diminished when Jefferson implemented the Embargo Act in response to British threats to U.S. shipping. The same year, Jefferson signed the Act Prohibiting Importation of Slaves. After retiring from public office, he founded the University of Virginia.