[2] Following consultations between the Engineer-in-Chief of the BEF, Brigadier George Fowke, and the mining specialist John Norton-Griffiths, the War Office formally approved the tunnelling company scheme on 19 February 1915.

[3] To make the tunnels safer and quicker to deploy, the British Army enlisted experienced coal miners, many outside their nominal recruitment policy.

These companies each comprised 5 officers and 269 sappers; they were aided by additional infantrymen who were temporarily attached to the tunnellers as required, which almost doubled their numbers.

[2] The success of the first tunnelling companies formed under Norton-Griffiths' command led to mining being made a separate branch of the Engineer-in-Chief's office under Major-General S.R.

[4] The formation of twelve new tunnelling companies, between July and October 1915, helped to bring more men into action in other parts of the Western Front.

Five days later they relieved the French 7/1 compagnie d'ingénieurs territoriaux in the "Labyrinth" sector of the Western Front between Roclincourt and Écurie in northern France.

[1] On 15 November 1916, the New Zealand Tunnelling Company ended its offensive mining operations[5] and started preparations for the Battle of Arras (9 April – 16 May 1917).

The underground quarries were to be linked up by tunnels so that they could be used both as shelters from the incessant German shelling and as a means of conveying troops to the front in secrecy and safety.

[6] The tunnellers named the individual quarries after their home towns (Auckland, Wellington, Nelson, Blenheim, Christchurch, Russell and Dunedin for the New Zealanders, and Glasgow, Edinburgh, Crewe and London for the Britons).

Assault tunnels were also dug, stopping a few metres short of the German line, ready to be blown open by explosives on the first day of the battle.

After the end of the Battle of Arras in May 1917, the unit focused mainly on creating deep dugouts beneath British trenches, which was continued into the winter months.

On 21 March 1918, the New Zealand Tunnelling Company was present at Arras during the large German spring offensive, and began work on trenches south-west of the town.

[5] On 15 July 1918, the New Zealand Tunnelling Company arrived at Marieux on the Somme, where it began constructing dug-outs beneath the British trenches.

[5] The New Zealand Tunnelling Company was next involved in the Battle of Havrincourt, opening on 12 September 1918, which began the German retreat back to the Belgian border.

This company had already suffered severe casualties building a ramp down the face of a retaining wall into the dry Canal du Nord.

Now, under VI Corps Troops RE,[13] the two companies (14 officers and 310 men in total) built a Hopkins steel bridge across the canal between Hermies and Havrincourt.

[14] In the autumn of 1918, the unit constructed further military bridges[5] that allowed the Allied troops to cross three main river obstacles: the Canal de l'Escaut, crossing Cambrai and going to the Canal de Saint-Quentin on the south, the Selle and the Ecaillon, two parallel rivers, separated from only two or three miles, in the southwest of Quesnoy.

The New Zealand Tunnelling Company reinstalled the communication roads and railways above natural obstacles at Noyelles-sur-Escaut, Masnières, Cambrai, Solesmes, Saint-Waast and Romeries.