On the first day of November, 1915, Mackensen could really say that he had conquered all of northern Serbia. But the fact remained that the Serbian army was still in the field; not even a part of it had as yet been captured or annihilated. And it is a military axiom that no matter how far an army may retreat and no matter how much territory may have been conquered, no battle is decisive until the enemy has been destroyed, either entirely or in large part. The Germans were to be reminded of this fact more than once on the Russian front. Up till this time Boyadjieff, at the head of his Bulgarian army, was attacking the Serbians from two directions: along the Timok against Kniashevatz, Zaichar, and Negotin, and along the Nishava against Pirot. Both movements were directed ultimately toward Nish, but the more northerly had also the purpose of effecting a junction with the left wing of the Germans under Gallwitz, which was advancing from Tekia, in the northeast corner of Serbia. Negotin and Prahovo, the latter a port on the Danube, had been taken on October 25, 1915. Lower down, the Bulgarians, who were in overwhelming strength, occupied both Zaichar and Kniashevatz on the 28th. Meanwhile, the Serbians were also compelled to abandon the commanding heights of Drenova Glava, fifteen miles northwest of Pirot, and on the 28th Pirot fell, though not without heavy fighting. With Pirot on the south and Kniashevatz on the north in the hands of the Bulgarians, the situation of Nish became very precarious. The Serbian Government was now shifted to Kralievo. Down in Macedonia the Second Bulgarian Army, under Todoroff, seemed to have come to an end of its initial success. After its occupation of Uskub it had advanced to Katshanik Pass, which was occupied by the Serbians under General Bojovitch. Todoroff at once began a violent attack and by October 28, 1915, part of the defile seemed to have been cleared of the Serbians. But presently the Serbians were reenforced by two regiments of the Morava Division and two of the Drina Division, whereupon Bojovitch suddenly turned and once more possessed himself of the pass. Again and again the Bulgarians attacked, determined to take the pass, but as often as they hurled themselves up the defile, just so often the Serbians drove them back with fire and bayonet. During this same period another Serbian force under Colonel Vassitch was fighting farther south. On October 22, 1915, he succeeded in recapturing Veles, which, it will be remembered, Todoroff had taken in his rapid advance during the first few days of his fighting. Here it was that the Serbians expected to make a juncture with the French forces under Sarrail, and for several days they could even hear the thunder of the French guns repelling a Bulgarian attack, so close together were they.