The so-called Peace of Amiens in 1801 proved to be only an interlude in the wars of France with Europe. Within two years hostilities were renewed which closed only with the battle of Waterloo. In the course of this prolonged conflict Napoleon won and lost for France the ascendency in central and western Europe, but Great Britain remained throughout mistress of the seas. The commerce of France and of Holland and Spain, which had become virtually her dependencies, was almost driven from the seas. For their foodstuffs and colonial supplies, more than ever in demand as war devastated the fields of Europe, these nations had to look to vessels flying neutral flags. The export trade of the United States, which had fallen from $94,000,000 in the year 1801 to $55,800,000 in 1803, rapidly recovered until in 1805 it passed the high-water mark of the earlier year. More than half of this trade was in products of the tropics, for while the direct trade between the West India colonies and Europe was forbidden by the so-called "Rule of 1756," American shippers carried on a lucrative traffic which was virtually direct. Products brought from the West Indies to American ports were promptly reshipped as part of American stock to European ports; and the British courts had held that this importation had broken the voyage. When once import duties had been paid in an American port, the courts refused to inquire what thereafter became of the cargo and whether in fact rebates were given on exportation. In midsummer of 1805 occurred a reversal of British policy. In the case of the Essex, which had made the voyage from Charleston to London with colonial produce from Martinique, a British admiralty court ruled for the first time that the payment of import duties was not sufficient proof of _bona fide_ importation, because of the practice in the United States of repaying duties on exportation. Other seizures followed that of the Essex, to the consternation of American shippers. Insurance rates on cargoes were doubled and doubled again within a year. Early in 1806, Monroe, then Minister to England, wrote in protest to the British Ministry that "about one hundred and twenty vessels had been seized, several condemned, all taken from their course, detained, and otherwise subjected to heavy losses and damages." But Monroe could not obtain any concession of principle or promise of indemnity.