The digging of underground tunnels took another week.
In the process the Ottomans launched four waves of attacks as a smoke cover up for the digging with troops from the tributary states, all halted by the moat, dropping down some two hundred bodies and scattered away, unable to step a little bit further.
Mehmed did not expect them to do anything progressive for the siege anyways, their sole purpose is to cover the friendly forces' actions with their body, that is what tributary troops are used for. However, the tunnel digging was also not as smooth as what he has expected.
Three tunnels came across severe geographical challenges like large Mélange of underground rocks consisting of Diabase stones which is near impossible to mine through with only pickaxes and human power, thus one tunnel was forced to change direction of digging while the other two had to abort the operations after speculations say that it will end up as a futile work. The Pasha in charge of digging, Ishak Pasha, had four heads chopped and send rolling to warn other peasants to not neglect their honourable work for the Sultan.
However this is hardly the worst piece of news for the day, of the other six tunnels digging, four tunnels dug their way straight into the moat before the Theodosian walls instantly flushing the tunnels with water, drowning the hundreds of miners inside digging, and most importantly because of the flooding ,the soil underneath became damp, moist and soft causing a catastrophic land subsidence. It is the worst not because it wasted hundreds of human lives, Mehmed do not care about the lives of some peasants, nor because of the time. It is the worst thing to happen because it revealed the strategic intent of the Ottomans to the Romans inside the city.
That is why sometimes you just have to get someone professional and leave the job to them, or else the outsider with the wrong profession might mess the thing up at the end of the day.
Lucky for Mehmed there are still hopes through the impenetrable Theodosian walls, the other two tunnels are being dug by hundreds of professional Serbian miners who knows very well on how to dig and where to dig. They successfully evaded the moat and rocks that are hard to mine, almost reaching the area below the Theodosian walls.
But what unlucky for him is that Constantine and Giovanni already have a plan to counter this.
Giovanni has this guy called John Grants in his band, a Scottish, but somehow joined a band of mercenaries led by a Genoese. He has a talent for engineering and architecture and with these skills and talents he came up with a set of skills that are specifically targeted to counter these undermining tricks by attackers in a siege.
John Grant had hundreds of barrels of waters placed on the ground a distance away from the walls, then he will have people on guard at all time observing the waves of the water surface. If there is a consistent circle of waves appearing on the water surface, it means that there is something in action under the ground.
With this tiny piece of trick, John Grant is able to locate where the rest of the tunnels is, then he and a bunch other citizens who chose to sign up on this task voluntarily, would start digging from inside the walls at an opposite direction towards the Ottoman camp at a correct altitude, which after a while of digging he will be able to catch the tail of these sneaky miners, by then a bunch of other mercenaries in light armour would be already there waiting for them with blades in their hands.
The Ottoman miners digging underground knew something is not right when pebbles started dropping on their head, and as they look up, they see light.
Light, definitely not what a miner should see in the middle of a digging operation. Then, a hole appeared and the plate-like, hair-raising face of John Grant popped up holding a lumberjack's axe. John Grant bulged his eyes, his face starting to turn red with sweat from hours of digging, and he greeted the miners with a sinister grin on his face using English.
"Here's Johnny~"
Before the miners could react further, some other mercenaries started pouring a kind of greasy black substance into the tunnels laughing, while John Grant pointed towards the miners and continued swaggering.
"You are already dead!"
"What?!" Wheezed the miners.
A miner had a taste of the substance, realised what is it, and immediately started yelling and warning other miners. "It is crude oil! Run lads! For your lives!" Then he started to be the lead and staggered towards the Ottoman side of the tunnel, the others soon started panicking and followed the miner trying to make a run for their lives out of this place that will soon become inferno sooner or later.
Of course, John Grant would not give them the chance of doing so, he dropped a fire torch into the tunnel which is like a circular that announced their fate. The moment the torch came into contact with the black crude oil, a series of violent chemical processes which sent the entire tunnel blasting upside down, the fire formed in the explosion traveled in an incredible speed like a phoenix, shrieking as it tears down all the miners in front who tries to stop her.
Within a minute or two the entire tunnel is literally wiped out of oxygen all consumed to support the fire; a life-free vacuum is formed in the tunnel leaving no creatures still alive inside, not even bones. The flames and high temperatures have already sparked them turning them into human compound matters, or in simpler words, ashes. Since they are already underground it saves the time for a burial too.
Mehmed's face turned stern green as he watches the phoenix of flames leapt out of the tunnel into the shaft burning it down too.