The investment of Maestricht was commenced upon the 12th of March, 1579. In the city, besides the population, there were two thousand peasants, both men and women, a garrison of one thousand soldiers; and a trained burgher guard; numbering about twelve hundred. The name of the military commandant was Melchior. Sebastian Tappin, a Lorraine officer of much experience and bravery, was next in command, and was, in truth, the principal director of the operations. He had been despatched thither by the Prince of Orange, to serve under La None, who was to have commanded in Maestricht, but had been unable to enter the city. Feeling that the siege was to be a close one, and knowing how much depended upon the issue, Sebastian lost no time in making every needful preparation for coming events. The walls were strengthened everywhere; shafts were sunk, preparatory to the countermining operations which were soon to become necessary; the moat was deepened and cleared, and the forts near the gates were put in thorough repair. On the other hand, Alexander had encircled the city, and had thrown two bridges, well fortified, across the river. There were six gates to the town, each provided with ravelins, and there was a doubt in what direction the first attack should be made. Opinions wavered between the gate of Bois-le-Duc, next the river, and that of Tongres on the south-western side, but it was finally decided to attempt the gate of Tongres. Over against that point the platforms were accordingly constructed, and after a heavy cannonade from forty-six great guns continued for several days, it was thought, by the 25th of March, that an impression had been made upon the city. A portion of the brick curtain had crumbled, but through the breach was seen a massive terreplein, well moated, which, after six thousand shots already delivered on the outer wall--still remained uninjured. It was recognized that the gate of Tongres was not the most assailable, but rather the strongest portion of the defences, and Alexander therefore determined to shift his batteries to the gate of Bois-le-Duc. At the same time, the attempt upon that of Tongres was to be varied, but not abandoned. Four thousand miners, who had passed half their lives in burrowing for coal in that anthracite region, had been furnished by the Bishop of Liege, and this force was now set to their subterranean work. A mine having been opened at a distance, the besiegers slowly worked their way towards the Tongres gate, while at the same time the more ostensible operations were in the opposite direction. The besieged had their miners also, for the peasants in the city had been used to work with mattock and pickaxe. The women, too, enrolled themselves into companies, chose their officers--or "mine-mistresses," as they were called--and did good service daily in the caverns of the earth. Thus a whole army of gnomes were noiselessly at work to destroy and defend the beleaguered city.