France, led by Napoleon, vindicated Adams's limited war policy by agreeing to settle the commercial policy dispute. The Convention of 1800 with France and the temporary cessation of hostilities in Europe combined to create a period of calm before the accession in March 1801 of Thomas Jefferson to the presidency. Some Federalists at the time and some historians since have portrayed the Louisiana Purchase as a stroke of diplomatic luck that owed little to Jefferson's presidential leadership. Jefferson's war on Barbary piracy represented a similar expansion of both the imperial reach of the United States and the power of the executive to make war. On June 22, 1807, the British warship HMS Leopard, patrolling the lower Chesapeake Bay, overtook and broadsided an American frigate, which was en route to the Mediterranean to take part in the Barbary War. Jefferson saw the embargo as a means of bringing back the self-sacrifice and patriotism that epitomized 'the Spirit of 76'.