Infantry Training 1937 states that the role of mortars in defence is:
i) Support counter attacks – for this role the mortar should remain with the support platoons. Mortars could also be used to force the enemy from a position which he has occupied by concentrated fire which could then be re occupied by patrols.
ii) To form a reserve of fire – the battalion commander can use the mortar to supplement his fire plan at any point which is proving ineffective or to break up enemy formations which have penetrated the defence.
iii) Defensive fire – they may be included in the fire plan of the defence to deal with some part of the front which is not adequately covered by other weapons. In such a role they could be laid on fixed lines.
Each battalion had a mortar platoon which consisted of a HQ and two sections, each of two mortar detachments. The platoon would be commanded by a subaltern, the section by a sergeant and the detachment by a corporal. Each detachment consisted of an orderly and five mortar members. The fire unit was the detachment (one 3” mortar). In addition, each infantry platoon would have the smaller 2” mortar (see section ‘Infantry in Defence’).
However due to BEF equipment losses in France, many battalions were short of mortars in 1940. The War Diary of 2/4 South Lancs notes that in April 1940 the rifle companies had no 2” mortars and the mortar platoon no mortars. By July it had 12 2” mortars but still no 3” mortars. When the battalion left Suffolk it did have its full compliment of 2” and 3” mortars. Older pre-Second War 6” mortars were frequently used to equip the mortar detachments until a full compliment of 3” mortars was received.
The role of the mortar platoon is illustrated with examples from two Defence Schemes. On ‘Action Stations’, 9th Lancs Fusiliers would have deployed two 6” mortars to battle positions to add to the defence fire plan by covering the beach between Aldeburgh and Thorpeness. Two 3” mortars were to proceed to Battalion HQ as part of the mobile reserve. The Defence Scheme of 11 Highland Light Infantry also notes the role of mortars as part of the defence fire plan with one 6” and one 3” in fixed positions at the Hill 50 defended locality.
Of interest is a comparison of the allotment of mortar ammunition to two battalions, one in 1940 and the other 1941. As at September 1940, 7th Manchester’s had:
3” – 159 H.E and no smoke
2” – 568 H.E and 294 smoke.
As at 14th August 1941, 6th Kings Own Scottish Borders had:
3” – 1,350 H.E and 450 smoke
2” – 1,296 H.E and 432 smoke
Above left and right: Home Forces training with 3" Mortars
Infantry Training 1937, W.O., 1937
7th Manchester’s, 11 HLI, 9th Lancs Fus., 2/4 South Lancs papers, TNA