Julius Caesar noted the smelting of iron on the Weald by native Britons at the time of his invasion. The Romans continued the industry, but it was discontinued after the Saxon invasions and not revived until the Medieval period. The blast furnace was pioneered in Belgium, with its first recorded use in England at Buxted near Uckfield (1490). The furnace forge required plentiful supplies of water and charcoal to refine the iron, and clay for the furnace walls. By the middle of the 16th century perhaps 50 such furnaces were operating in the Weald, supported by extensive ancillary industries mining the ore and felling timber. Initially, production concentrated on the bloomers of pig-iron for onward manufacture but by the late 16th century, armaments, particularly cast-iron cannon, were being produced locally. By the early 1600s, at its peak, over 100 furnaces dotted the Weald. Thereafter a slow decline began through foreign competition, most notably from Sweden.