The Hohenzollern Redoubt was a German defensive position north of Loos-en-Gohelle (Loos), a mining town north-west of Lens in France.

Over the winter of 1915–1916, the 170th Tunnelling Company RE dug several galleries under the German lines in the area of the redoubt, which had changed hands several times since September 1915.

No man's land had become a crater field and the Germans had an unobstructed view of the British positions from the Fosse 8 slag heap.

The British front line was held by outposts to reduce the number of troops vulnerable to mine explosions and the strain of knowing that the ground could erupt at any moment.

The recovery by the Germans of the gallery entrance threatened the positions captured by the British, who attacked Triangle Crater on 6 March and were repulsed.

The German attack had nearly as much success as that of the British on 2 March, forcing them back to the original front line, before local counter-attacks regained some of the craters.

The Germans had an unobstructed view of the British positions, from a slag heap called Fosse 8 and in previous mining operations no man's land had become a crater field.

The British front line was held by outposts, to reduce the number of troops vulnerable to mine explosions and the strain of knowing that the ground could erupt at any moment.

There had been much snow, sleet and rain during the week previous and the attackers found that in the displaced earth from the mine explosions, they were shin deep.

Twenty men from a supporting unit joined the two survivors but The Chord had mostly been destroyed in the area, leaving little cover.

[9] The 170th Tunnelling Company followed up the infantry and began to blow up the German gallery entrance found in Triangle Crater.

The failure of the attack and the vulnerability of the start line, was reported at 6:55 p.m. and a company of the 6th Battalion, Royal West Kent was sent forward.

The reinforcement and the divisional artillery, managed to repulse the German counter-attack but from 6–7 March, the 37th Brigade lost 331 men.

German attacks on the craters continued but were defeated, despite restrictions imposed on British artillery ammunition consumption.

German artillery-fire increased in the morning and fire from trench mortars caused a great deal of damage.

[17] The troops of the 6th Buffs in craters 1, 2 and A, were killed or buried and the confusion was made worse because West Face Trench, Saville Row and Saps 9 and 9a had been filled by the debris thrown about by the bombardment.

Five mines detonated short of the British lines at 6:15 p.m., causing a certain amount of disorganisation and dismay in III Battalion, Bavarian Infantry Regiment 23, which then rallied and commenced the attack.

The Bavarians recaptured The Chord and pushed back the 37th Brigade to the near lips of the craters and the old British front line.

A British counter-attack was delayed by the need to clear the saps and then three companies of the 6th RWK recaptured the near lips of the craters.

The craters attracted artillery and mortar fire but gave no protection, being confined spaces with a morass of liquid chalk and black mud at the bottom, which was unusable as a material for fortification.

Defending the forward lip had proved difficult, due to its breadth and the presence of clay mounds 12–20 ft (3.7–6.1 m) high, which obstructed the field of fire.

Each explosion was followed by infantry attacks and consolidation of the mine lips, which were costly to both sides and turned more areas of no man's land into crater fields.

The 12th (Eastern) Division was relieved on 26 April and missed the German gas attack at Hulluch, which began the next day.

The gas cloud and artillery bombardment were followed by raiding parties, which made temporary lodgements in the British lines.