Editing Field Marshall (section)

==Earlier Marshall tractor line ==
[[File:Marshall tractor 10621.JPG|thumb|1942 Marshall Type M tractor]]
The first single-cylinder Marshall tractor to be introduced was the Marshall 15/30 in 1930. It had a {{convert|8|in|mm|adj=on }} bore with a {{convert|10|in|mm|adj=on }} stroke (=  8.237 litres) and the maximum speed was 550 r.p.m., or 9.1666 revolutions per second.
In 1932 the 15/30 was upgraded to become the Marshall 18/30. This model featured the same bore and stroke dimensions but the maximum r.p.m. was increased and the tractor's transmission was heavily modified.

The next single-cylinder Marshall to be introduced was the Marshall 12/20 in 1935. This tractor was of a completely new design, with a {{convert|6|in|mm|adj=on }}-inch bore and a {{convert|9|in|mm|adj=on}} stroke (= 4.17 litres). There were many smaller modifications such as a redesigned injection pump and cylinder head.

In 1938 the 12/20 model was redesigned and the model coding was changed so that the new model became the Marshall Model "M" tractor. During World War II tractor production was reduced greatly due to Marshall's factory capacity being engaged on war work. However, after the war, in 1945, Marshall's of Gainsborough introduced the improved diesel-powered tractor they had developed as the "Field-Marshall".<ref>{{cite web|url=http://tractordata.co.uk/field_marshall/|title=Marshall & Field Marshall Tractors|publisher=Tractor Data|accessdate=9 December 2017}}</ref>