In the year 1812 war broke out between Great Britain and the United States. For a time the continental warfare had led to a great increase in American commerce, which was free from the attacks of privateers and from the restrictions which the opposing parties placed on one another. Presently, however, both parties attempted to force the United States into a virtual alliance with themselves. Orders in council on the one side and imperial decrees on the other had, as we have seen, declared a blockade of the ports of the continent of Europe and of Great Britain, and the United States saw their commerce threatened with disabilities approximating to those suffered by the belligerent powers. President Jefferson, who was supported by the republican party, adhered to a policy of strict neutrality, and prepared to suffer any commercial loss rather than be drawn into an European war. The only action which he took was the defence of the river mouths with a view to resisting any offensive movement. The federalist party on the other hand were in favour of energetic action against France, so as to secure English favour and the great commercial privileges which the mistress of the seas could bestow. For a time no hostilities resulted, but constant irritation was caused by the British claim to a right of search and to the impressment of sailors of British nationality found on American ships, while American ships accused of infringing the blockade were seized by either of the European combatants. To some extent the differences between Great Britain and the United States depended on rival views of the law of allegiance. The British maintained the doctrine _nemo potest exuere patriam_, and regarded all British-born persons, unless absolved from their allegiance by the act of the mother-country, as British subjects. The law of the United States, on the other hand, permitted an alien to become a citizen after fourteen years' residence, and previously to 1798 had required a residence of five years only. In this way it often happened that sailors who had received the American citizenship were impressed for service on British ships, and sometimes sailors of actual American birth were impressed. But it was impossible to justify the practice to which the Americans resorted of receiving deserters of British nationality from British ships of war, who were induced by offers of higher pay to transfer themselves to the American service.