The method was safer than open sapping, although in due course the Turks became aware of the work through sound and by discovering the ventilation holes:

About 11pm tonight a Turk shoved his hand down the air hole in the drive just opposite me. It scared the wits out of us all. We could hear them crawling around above us all night. The men in the firing line evidently shot one, as we could hear him groaning just above us. (Lance Corporal Cyril Lawrence, 2nd Field Company, Australian Engineers, 15 June 1915)¹⁶

In early June General Walker, temporarily commanding the 1st Australian Division, decided to make a new forward line underground along most of the right Central Sector of Anzac. Also in June, a semi-underground system to extend the front line was adopted for the right sector. At Tasmania Post on the southern part of the Anzac position, a number of short tunnels were driven forward at the request of Lieutenant Colonel Smith, commanding the 12th Battalion, in order to gain a view into the Valley of Despair, a steep gully in front of the position. These ended in ‘bombing-holes’, openings in which sentries were stationed and barbed wire put out. Two of the tunnels were continued towards the Turkish trench without encountering Turkish countermining. Smith suggested to Brigadier General MacLagan (commanding 3rd Australian Brigade) that the mines could be blown and the tunnels used as communication routes to aid an attack to take the Turkish trench on the edge of the valley. General Birdwood, commanding the Anzac Corps, took up the proposal, as the attack could serve as a feint to distract from the coming Suvla Bay landing. When the Turks extended their position opposite Tasmania Post north, the Australians lengthened two more of the bombing-hole tunnels towards their trench. MacLagan asked Birdwood for two days extra to complete the tunnels and an attack using these galleries was fixed for moonrise of 31 July 1915. In a carefully planned assault, four mines were to be fired from the tunnels and an assault made by the 11th Battalion, led by Captain Leane. The tunnels would then be opened up to allow reinforcement of the captured Turkish position.

The mines were to be fired at zero but, at the signal, only the two outer mines detonated. Leane nevertheless led his men forward and, as they reached the Turkish trench, the southern of the two central mines blew, burying small numbers of both Turks and Australians, and parties of men reached the Turkish trench with debris still raining on them. The fourth mine never exploded, but the Turkish troops left their trench on being attacked. While the trenches were assaulted the four mine tunnels were opened into the craters for communication use, with parties of infantry digging from both directions in the tunnels and the craters. The air in the tunnels was found to be sufficiently pure, the explosive gases having vented through the crater, and within an hour three were clear enough to allow some supplies to be passed through into the craters. It was not possible to get men through the tunnels until the early morning and during the night they crossed the open: by the small hours three were open for communication. The congestion in the tunnels, however, was apparently the reason that water stored ready in Tasmania Post was not taken forward. The captured position, named Leane’s Trench, was held against Turkish counterattacks and the use of tunnels for communication, like the blowing of mines, had been a partial success.

Birdwood issued orders for another small attack against a post in front of Ryrie’s Post, immediately south of Tasmania Post. The tunnels were regarded as sufficiently essential to the attack for it to be indefinitely postponed on 5 August on the objections of the OC 3rd Field Company, Major Clogstoun. Clogstoun reported that his tunnels were unlikely to reach the Turkish trenches by the date of the attack and that, unlike at Leane’s Trench, the Turks were already mining in front of Ryrie’s. If the position was captured it would be unlikely that full communication using tunnels would be established in less than eighteen hours and, as the area was swept by Turkish flanking fire, it was doubtful whether the attackers could hold out that long.

A more ambitious use of tunnels for the attack was already in hand at Lone Pine using the underground front line formed from the B Group tunnels as a diversion from the breakout attack being made north from Anzac. Seven saps were linked by a transversal to form the underground front line and two, B5 and B6, were extended to form galleries for offensive mining. The assault on Lone Pine on 6 August was to be a more ambitious version of that on Leane’s Trench and troops were actually to assault from the tunnels. Three battalions were to attack and the leading company of each was to depart from the underground firing line just 40 to 60yds from the Turks. The tunnels were widened and the space required by each battalion was carefully worked out. In its methodical timing the Lone Pine operation resembled a French sapping and mining assault of early 1915. The infantry were to assault at 5.30pm but, probably because of the complexity of the operation, the preparations were phased. The engineers began opening the exits the night before and completed the task three and a half hours before zero. At this time three mines were blown in no man’s land in order to create some cover for the attackers.¹⁷ The preparatory bombardment was carried out during the afternoon and was augmented one hour before zero by fire from heavy naval guns offshore.