The tactical role of the medium machine gun in defence is summarized in Infantry Training 1937. The machine gun is the most powerful infantry weapon of defence as it is capable of producing a concentrated volume of accurate and sustained fire beyond the range of rifles (and light machine guns) and yet only presents a small target in action.
Machine guns had a great length of beaten zone relative to its width (the beaten zone arises due to the fact that every bullet fired would not hit the exact same spot), which means they are best deployed to fire obliquely or enfilade relative to the target. To be fully effective, machine guns must be able to maintain their fire in all conditions. Therefore in defence they were given an arc of fire and fixed lines of fire (when fire could be maintained even if observation of the target was not possible e.g. at night). Targets within the arc of fire would always receive priority but the gun, at its commander’s discretion, could engage targets outside its defined arc.
In defence machine guns were organized in depth and sited to cover with oblique or enfilade fire the probable lines of enemy approach to provide as far as possible a continuous belt of fire. The fire plan would be closely co-ordinated with light machine guns (which could also fire on fixed lines when mounted on tripods) as well as rifle posts and the artillery. Positions for machine guns would be chosen with the following considerations: a covered approach, concealment and cover and facilities for ammunition supply
Medium machine gun support was provided by machine gun battalions. These were orgainised into a HQ Company and four machine gun companies. Each machine gun company had three M.G platoons, each platoon two sections and each section two machine guns. In Suffolk, machine gun support was first provided (to 55th Division) by the P.L Kensington Regt at the strength of between one platoon to company per infantry battalion. The battalion arrived in Suffolk on Jul 4th and all guns were to be in position by Jul 6th. Ammunition was 21 belts per gun with 10 belts per gun held in Battalion reserve. At first gun crews were accommodated in tents next to gun positions. Sandbags were available for emplacements and overhead cover against machine gun bullets consisting of corrugated iron and two layers of sandbags was considered sufficient. Slit trenches were also to be dug. It was planned to build concrete pillboxes when the gun positions were finally approved. At least four shell proof pillboxes were specifically constructed for gun positions – Blythburgh (two), Dunwich and Benacre
Above: Shell proof pillboxes for the Vickers Medium machine gun - Blythburgh
The 4th Cheshires were in support of 42nd Division. The War Diary of 125th Brigade notes that the Vickers guns of the 4th Chesires were to be withdrawn to form a line, along with 2 pounder anti-tank guns, 2,000 - 3,000 yards in the rear of the beach defences. To replace the guns withdrawn American Vickers .300 guns were to be issued and manned by the infantry. The War Diary notes on 12th Jan 1941, 17 American guns were received with 1,500 rounds each which was considered entirely inadequate.
In 1941 the MG battalion in support of 15th Division was 2nd Middlesex Regt. The 2nd Middlesex had a total of 46 machine guns in 1941. These troops would come under the command of the front line infantry company commanders in the event of enemy attack. The War Diary of 15th Division notes the new role of medium machine guns to add depth to the defence - medium machine guns "will be sited primarily to provide depth to the defence both against troops that have penetrated from the beaches and against airborne troops landed in the rear of defended localities".
Vickers (medium machine gun) on training exercise Bren Gun (light machine gun) - the fire plan of the medium
machine gun companies would be closely co-ordinated
with the infantry companies light machine guns
Infantry Training 1937, HMSO, 1937
F.S.P.B Pamphlet No 1, HMSO, 1940
125 Brigade papers, TNA