In the attack, the fundamental principle of fire and movement infantry tactics at sub-unit level as taught by the Battle Schools was that of keeping ‘one leg on the ground’. Essentially, this meant that one infantry group would either be firing or down in a position from which fire could be instantly opened, while another group would be moving forward, making use of whatever natural cover was available to conduct a flanking attack. If executed effectively, this practice would ensure that the enemy were forced to keep their heads down and thus unable to open fire on the manoeuvring group. This would allow the attackers to get close enough to make the final assault. To achieve success with these tactics, British and Canadian soldiers needed skill, courage and a high level of physical fitness. More importantly, they required weapons with sufficient weight of fire to have a reasonable chance of either suppressing or killing the opposition.

In 1944, a full strength infantry section in 21^st Army Group would consist of a Section Leader, equipped with a Sten sub-machine gun, a Bren gunner and eight riflemen. It had long been recognised that the magazine-fed and gas-regulated Bren Light Machine Gun was the “principal fire producing weapon of the section”. It was a reliable and trustworthy firearm, which was well regarded by those who used it, and has been subsequently lauded as one of the finest light machine guns ever made. Such was the importance attached to the firepower provided by the Bren, ensuring that there was enough ammunition to keep it in action was a serious concern. Each magazine had a capacity of 30 rounds, though this was usually reduced to 28 in practice in order to avoid feeding problems. In addition to the thirteen magazines carried by the typical three man Bren team, the remaining riflemen in the section carried a further two magazines each, giving a total of twenty-five. This led to the view, expressed by an officer at an infantry training conference in April 1945, that “In attack, the rifleman seldom uses his rifle, being mostly employed as amn (ammunition) carrier for the Bren”.

It was certainly expected that the Bren gun on its own would produce almost half of the total firepower of the section. In 1944 a study was carried out by the Army Operational Research Group (AORG) on the amount of small arms fire needed to neutralise various targets. Although the results obtained were deemed 'exceedingly tentative', the report’s assumptions and conclusions throw an interesting light on the level of firepower required to suppress an enemy position. To achieve 'heavy neutralisation' (defined as the weight of fire needed effectively to stop any retaliatory measures on the part of the enemy) of a target located in slit trenches, on a frontage of twenty yards and at a range of between one and two hundred yards, two hundred rounds of small arms fire per minute would need to be laid down. This could comfortably be achieved by a full strength infantry section on the assumption made in the report that the Bren would produce a rate of fire of 120 rounds per minute and each rifleman 18 rounds per minute. With the Bren’s theoretical maximum rate of fire of up to 500 rounds per minute, the Research Group’s findings support the view that the small arms carried by the infantry section were more than adequate to do the job required of them.

Doctrinal factors also played a part in limiting the amount of firepower at the disposal of the Commonwealth infantry forces. Although the School of Infantry taught and encouraged a very high rate of fire, particularly from troops armed with the rifle, other sources of information disseminated to soldiers in the field stressed the need to conserve ammunition and exercise correct fire control. The instructions in the Small Arms Training Manual for the use of light machine guns were explicit: “…the gunner will invariably fire single rounds”, although short bursts were also permitted when appropriate. The reasons given for this approach were threefold – it conserved ammunition, made location by the enemy more difficult and produced greater accuracy of fire. A further consideration was the belief that, if the target were not hit in the first burst, the enemy would go to ground anyway and subsequent bursts would not be so effective. However, the principal driver governing the parsimonious use of firepower in the assault was the concern, widely expressed among infantry commanders, that heavy expenditure of ammunition in securing the objective would make repulsion of the inevitable German counter-attack difficult if not impossible. This was clearly stated at the Infantry Training Conference in April 1944 when one delegate complained: -

“It is considered that present teaching lays too much stress on the use of infantry weapons in the attack, especially the Bren. Experience shows that the ammunition problem is acute in the counter attack phase. Ammunition fired in the attack is seldom aimed and therefore wasted”.

This view was shared by senior commanders. Lieutenant General Simonds’ directive to infantry not to open fire in the assault (see Article 4) was, to a large extent, influenced by the requirement to have enough ammunition for defence.

A further difficulty faced by 21^st Army Group infantry units in their attempts to lay down sufficient fire to achieve suppression of enemy positions was the superior firepower deployed by comparable German entities. By 1944, the German infantry squad carried a higher proportion of automatic weapons than a British or Canadian section. More importantly, its machine guns, the MG34 and MG42, were belt-fed weapons with a very high cyclic rate which could produce considerably more weight of fire than the Bren. Capable of firing long sustained bursts that pinned Allied soldiers to the ground, ‘Spandaus’ (as these weapons were universally referred to) were feared and respected in equal measure. Lieutenant Sydney Jary rated the Bren as excellent, but “…when it came to a fire fight between a German and a British platoon, their MG34 and MG42 won hands down”. Jary describes how an attack by the battalion on Mont Pinçon, 6^th August 1944 was “stopped dead in its tracks” by the fire of twelve German machine guns from the front and both flanks. So great and prolonged was the weight of fire that Jary was unable to locate the enemy firing positions. It is probable that the psychological impact produced by German machine-gun fire exceeded its physical effects; nevertheless, the ability of Spandau fire to pin down an attack was a major factor in preventing British and Canadian infantry from effectively neutralising enemy positions.

The 2-inch mortar was also a relatively ineffective anti-personnel weapon (although it was useful for producing smoke screens) and few infantrymen had much confidence in it. Indeed, trials conducted in 1942 showed that it had only a 10% probability of hitting a target at a range of 200 yards. Therefore, the crushing weight of fire desired by the infantry of 21^st Army Group would need to be delivered by the light machine guns.

Lionel Wigram had reached the same conclusion himself after witnessing combat in Italy. In his report of August 1943, Wigram proposed a simplified form of Battle Drill in which a platoon would be handled as a large section split into three groups – the three Bren gun teams, the remaining riflemen and the 2-inch mortar in support. The main intention was to focus enough suppressing fire from the Brens on to the German machine guns while the rifle section made their way straight to the enemy position. As long as the fire from the Brens was constant, this would “invariably silence” the enemy’s machine guns as “even inaccurate fire from our Brens will quieten the Spandaus until we have finished firing”. Wigram’s realisation that consistent and concentrated fire from the Bren guns at decisive points on the battlefield would give the doctrine of ‘keeping one leg on the ground” a fighting chance of success was also grasped by a number of commanders in Normandy and was the basis of many tactical and organisational innovations as the campaign progressed.

The provision of additional firepower to 21^st Army Group infantry units was often accompanied by a change in organisation and tactics. Hart-Dyke reorganised his platoons into two Bren gun sections of two NCOs and four men with two Brens each, one large rifle section, and a platoon headquarters with the 2-inch mortar. Tactics were modified so that, in the advance, Bren sections advanced up parallel hedgerows with one Bren covering the other, while the rifle section was held in reserve and available to execute a flank attack under the direction of the platoon commander. Hart-Dyke claimed that this approach, which was also highly successful in defence, was maintained by the battalion throughout the campaign and he and his men never had cause to regret it. In the attack on Troteval Farm, Major Dextrase dispensed with rifle groups within the platoons altogether. As he put it: -

“The No.2’s carried rifles and the section leaders carried Stens, but there were no rifle groups as such…The actual clearing of the farm was done with light machine guns and No. 36 grenades. The Brens were carried with a sling and when held firmly against the hip were as flexible as necessary”.

Although firing the Bren in this way compromised the accuracy of the weapon, this was not a serious disadvantage in engagements of this nature. In fact, an investigation conducted by the AORG in May 1944 found that 'traversing fire' (traversing the Bren over an arc without aiming at individual targets) produced more enemy casualties than firing short, aimed bursts at specific targets at ranges of up to 200 yards. In order to increase rates of fire even further, the gas regulator of the Bren would often be set at the largest hole.

The rifle companies of 21^st Army Group entered the Normandy campaign at a disadvantage in that their principal firepower producing weapon was inferior to its German equivalents, was not available in sufficient numbers and was hampered in its effectiveness by the need to conserve ammunition in the attack. However, as we have seen, several units, using their initiative and adaptability, made efforts to maximise the amount of firepower at their disposal.