The badly shelled main road to Bapaume through Pozieres, showing a communication trench and broken trees
The 34th Division, under the command of Lieut. General Sir W. P. Pulteney, was to advance on July 1st 1916, the opening of the British infantry assault of the Battle of the Somme.
On the front of the 34th Division two large and two small mines were ready to remove the heavily fortified German strong points such as the formidable strongpoint called 'Schwaben Höhe', which might be left in the enemy's front line despite the previous seven day bombardment by the British artillery.
For the 1 July 1916 attack two large mines were planned, one to the north of La Boisselle (Y Sap) and one to the south (Lochnagar). Both were 'overcharged' which means that more explosive was used than was necessary to just break the surface, so large rims were formed from the disturbed ground.
The tunnel for the Lochnagar mine was started on 11 November 1915 by 185 Tunnelling Company, but was completed by 179 Tunnelling Company who took over in March 1916.
The objects of the mine were:
1. to destroy the enemy trench and dugouts and to knock out his machine guns at this point, where his trench formed a pronounced salient
2. destroy his underground system whatever it might be
3. to kill any troops he might have sheltering underground from our bombardment.