The poor quality of western European forests as sources of masts and the depletion of oak forests in Britain and France during the eighteenth century forced the two principal maritime powers to import naval timber and to seek far afield for naval masts. Both Britain and France gradually were forced to increase their imports of timber from neighboring states and the Baltic market. The acquisition of masts for naval vessels involved even greater dependence on markets overseas. Masting trees were sparsely scattered in western Europe; the British Isles produced none. France took some masts from forests in the Pyrenees, Auvergne, Alsace, and Dauphiné, but they were limited in quantity, lacking in flexibility, and were often condemned for their propensity to early brittleness and rot. Masts imported from French colonies in North America proved unsatisfactory in both cost and quality. Until the last quarter of the eighteenth century Britain enjoyed an advantage over France in the acquisition of colonial North American mast supplies, since die forests of New England produced excellent masts of extraordinary size. Britain's imports from New England, under a Royal Navy monopoly, satisfied a sizable part of her needs and reduced the British navy's importation of Baltic mast supplies by perhaps one third in the early 1770's. The American Revolution, however, abruptly ended Britain's monopoly of American masts. The rebellious colonists halted British imports and opened the splendid pine forests of New Hampshire, Massachusetts, and Maine to French naval exploitation.