In the Mlawa sector to the north of Przasnysz the Russians had developed an exceedingly strong system of fortified positions between their advance lines and the Narew fortresses. For miles, to a depth of from fifteen to twenty kilometers, there ran some three or four and at certain points even five systems of trenches, one behind the other. Hundreds of thousands of thick tree trunks had been worked into these defensive works and millions of sand bags piled up as breastwork. Bombproof dugouts had been constructed deep in the ground. Everywhere there were strong wire entanglements before the front, sometimes sunk below the level of the earth, arranged in from two to three rows. Projecting bastions and thoroughly protected observation posts gave these systems of trenches the character of permanent fortifications. The country in this region is hilly, with here and there steep declivities and peaks of considerable elevation. The Russians had cut down whole stretches of forest in order to afford them a free field for their fire and an opportunity to observe the advance of their opponents. Enveloping tactics on the part of the Germans were here quite excluded as the two lines ran uninterruptedly close to one another. Przasnysz which had become a heap of ruins had been converted virtually into a fortress by strong defensive works built while the Germans and Russians lay opposite each other in front of it throughout the spring. The country round about had been drenched with much German and Russian blood. General von Gallwitz, to capture a place with the least possible loss, decided to break through the Russian defenses at two points at both sides of the town sufficiently close to each other so that the intervening lines would be immediately affected. His attacks were therefore directed at the first line Russian positions, which formed projecting angles to the northwest and northeast of Przasnysz so that instead of taking the city directly from the front he would seize it as with a gigantic pair of pincers from both sides and behind. The plan succeeded to the full. The Russian lines were broken on both sides of the city and the German troops, rushing through, met behind it, forcing the Russian defenders hastily to evacuate the place to avoid being caught within the circle. Strong infantry forces were collected opposite the points of attack, and enormous masses of artillery were placed in position with abundance of ammunition in readiness. The preparations had been made with all possible secrecy and even when the German batteries had begun gradually to get their range by testing shots no serious assault seems to have been expected by the Russians. On the morning of the attack they were just to inaugurate service on a small passenger railway line they had constructed behind their front.