 They were created in the 18th and 19th centuries to augment the existing defences and protect the key port of Dover from both seaward and landward attack; by the start of the 20th century Dover Western Heights was collectively reputed to be the 'strongest and most elaborate' fortification in the country.The Army finally withdrew from the Heights in 1956-61; they are now a local nature reserve.First given earthworks in 1779 against the planned invasion that year, the high ground west of Dover, England, now called Dover Western Heights, was properly fortified in 1804 when Lieutenant-Colonel William Twiss was instructed to modernise the existing defences.