join his adventure. In October 1806, Jackson wrote James Winchester that the United States "can conquer not only the Floridas [at that time there was an East Florida and a West Florida], but all Spanish North America". He informed the Tennessee militia that it should be ready to march at a moment's notice "when the government and constituted authority of our country require it", and agreed to provide boats and provisions for the expedition. Jackson sent a letter to president Thomas Jefferson telling him that Tennessee was ready to defend the nation's honor. Jackson also expressed uncertainty about the enterprise. He warned the Governor of Louisiana William Claiborne and Tennessee Senator Daniel Smith that some of the people involved in the adventure might be intending to break away from the United States. In December, Jefferson ordered Burr to be arrested for treason. Jackson, safe from arrest because of his extensive paper trail, organized the militia to capture the conspirators. Jackson testified before a grand jury at Burr's trial in 1807, implying that it was Burr's associate James Wilkinson who was guilty of treason, not Burr. Burr was acquitted of the charges. Military career War of 1812 Creek War On June 18, 1812, the United States declared war on the United Kingdom. Though the causes of the War of 1812 were primarily about maritime issues, the war provided the white settlers on the southern frontier the opportunity to overcome Native American resistance to settlement, undermine British support of the Native American tribes, and pry Florida from the Spanish. Jackson immediately offered to raise volunteers for the war, but he was not called to duty until after the United States military was repeatedly defeated in the American Northwest. After these defeats, in January 1813, Jackson enlisted over 2,000 volunteers, who were ordered to head to New Orleans to defend against a British attack. When his forces arrived at Natchez, they were ordered to halt by General Wilkinson, the commander at New Orleans and the man Jackson accused of treason after the Burr adventure. A little later, Jackson received a letter from the Secretary of War, John Armstrong, stating that his volunteers were not needed, and that they were to be disbanded and any supplies were to be handed over to Wilkinson. Jackson refused to disband his troops; instead, he led them on the difficult march back to Nashville, earning the nickname "Hickory"