Between the wars, the moorland was only occasionally used by the military, mainly the 5th Somerset Light Infantry embodied as a territorial force.
. Mobilisation in 1939 saw this battalion become a major unit, and it served generally in West Somerset, until transferred in 1940 as part of anti-invasion preparations. The 9th and 10th Somerset Light Infantry were raised in this period and allocated to coast defence in the whole county. Parts of these units were stationed on the coast within the parish.
The moorland zone became a major military camp and training ground. All the high ground was place out of bounds to civilians and farms were evacuated. Units active in the area were specialised support groups rather than basic infantry or armoured battalions, but Canadian and American tanks used the area for training.
The cliff area was again considered for coastal defence purposes, and the coastline came under the command, firstly by the Portland Naval Base, and then the 20th Coast Artillery Group. At least two 4inch naval batteries were installed and the remains of their sites may still be seen. The whole area was militarised at this time with the construction of a light railway, roads, watchtowers, underground storage rooms and shooting areas. Activity delined before the end of the war and had ceased by 1946. A systematic program of removal of all military structures was started being formally completed by the early 1950s, when the area reverted to common land or the original owners. The general area was officially declared safe for public use, but bomb disposal parties were still operating in 1978.

Update, a lot of the foundations have just been uncovered and can be viewed here

Major evidence remaining includes foundations and buildings, the site of part of the light railway, possibly for moving targets, miscellaneous brickwork and land damage by tracked vehicles. Two old quarries were reopened by the military in 1939 for roadmaking. Mounds cover blocked-up underground chambers. The northern end of moor wood is covered with massive concrete aprons and various mounds and ditches all of military significance.
A bumper water supply with frequent standpipes was installed in 1935 along the length of North Hill. Most of the pipes were later removed, but one, just above Bramble Combe remains.