Tractor unit pulling an earth grading machine at a site near Rotherham South Yorkshire The AllisChalmers HDW TractorBulldozer was introduced in and approximately HDW units were used by the US military during World War II The HD continued to be manufactured until An identical machine can be seen in the background The HDW was the widetrack version of the HD with a inch gauge Models produced during World War II until sn had tracks with links and five rollers The reliability of the HDW in military service moved AllisChalmers forward as a producer of tractors following the war Keppels Column can be seen in the distance This is a folly built by John Carr in and named after Admiral Augustus Keppel in memory of his court martial acquittal