The “Donald Dinnie” was an excellent projectile when it burst in the right place. Sometimes, however, it did not burst at all, while at others it burst within a few feet of the mortar. Again, the mortar frequently misfired. Trench-mortaring was rather a game of chance in those days, with the odds slightly against the man firing the mortar.

In the early days of the “Donald Dinnie” its long iron handle, with a diameter of two inches, was firmly fixed to the bomb. On occasions this handle was blown tremendous distances by the explosion, and more than once fell in the British trenches, causing casualties to the garrison.

There was thus no adequate weapon with which to counter the German trench-mortars. He was therefore able to do considerable damage to our trenches and troops, more or less, with impunity.

It was in consequence necessary to institute a system of artillery retaliation, by which a certain number of rounds were fired back at the enemy by howitzers for every trench-mortar round he fired. Howitzers of various calibres up to 6-inch as well as the field-guns took part in these retaliatory shoots, according to the ammunition supply. As this became more liberal, this system tended to check the enemy’s trench-mortar activity, particularly when, by careful observation, the positions of his trench-mortar emplacements were located, and the retaliation was brought to bear actually on the offending mortars.

The enemy could, however, bombard certain sections of trenches so systematically that he was able to obliterate them. This was particularly the case opposite La Boisselle and in an area known as the Salient. The latter received so much attention as to become untenable, and on 1st December it was evacuated, a retrenchment being dug and occupied behind it.

During these trench-mortar bombardments, it had been discovered that the French shelters, having only three or four feet of cover, were not shell-proof. They were, in fact, death-traps, as they gave the men a false sense of security. In consequence, during a bombardment men would crowd into them to take cover, and should a trench-mortar bomb then strike one of them, it was blown in and all its occupants were killed.

On 21st October it was therefore decided to provide fresh dug-out accommodation for the whole garrison. The tunnelling company, as has been explained, was strained to its utmost to keep pace with the mining situation. The construction of the dug-outs was therefore entrusted to the 8th Royal Scots, who had joined the Division as the Divisional Pioneer Battalion on 25th August 1915. Fresh calls were made on the infantry for skilled miners, who were attached to the 8th Royal Scots. Work was carried on day and night, and the greatest exertions were made to provide the Division with shell-proof shelters with the minimum of delay.

These dug-outs were designed to give 10 to 12 feet of head cover. Charges of 60 lb. and 100 lb. of gun-cotton were exploded on the roofs of dug-outs of this depth, and the shock of the explosion was successfully resisted.[4]

Attempts were made to construct dug-outs by digging deep pits and then roofing them in with layers of material calculated to burst shells; but this was found to take more time than was required to construct a dug-out by tunnelling.

While the mining and the construction of dug-outs was being carried on as intensively as possible, an enormous amount of spoil (excavated earth and chalk) was accumulated. The disposal of this spoil became a very serious problem. Chalk cannot be scattered broadcast except at a distance from the shaft-heads, as its presence would disclose to the enemy that work was in progress and draw shell-fire. The accumulation of spoil was thus very difficult to dispose of, and frequently the trenches became almost impassable owing to the heaps of sandbags full of chalk stacked against their sides waiting to be emptied. The usual method of disposing of this spoil was to dump it into disused trenches and shell-holes. These, however, were soon filled, and it became evident that elaborate arrangements must be made beforehand for dealing with the spoil whenever operations entailing excavations on a large scale are planned, otherwise vast accumulations will be formed.