In August 1916 the Bulgarians launched the Lerin operation. The Entente troops started a counter-attack and on 30 September took Kajmakčalan with heavy casualties and continued to Bitola. In the area of the River Crna (Macedonian and , ) the Bulgarian 8th Tundzha Infantry Division had taken hastily defensive positions in September 1916. That division took the main enemy blow. On 5 October the Serbian troops made their first attempt to cross the river. Some of them reach the right bank but were counter-attacked by the Bulgarians and defeated and had to retreat. On 6 October the Serbs attack again near the villages of Dobroveni and Skochivir but were again counter-attacked and pushed back. The Bulgarians took the village of Brod. The Serbs who had great superiority in artillery attacked constantly. On 14 and 15 October 1916 the fights continued without interruption. The Serbian pressure was immense and the Bulgarians continued to hold their positions. During the night of 15 October was one of the culmination moments of the battle when the Serbs made 8 successive attacks which were all repulsed. The Serbs then recovered for three days and on 18 October they crossed the left bank of the River Crna at Brod and fortified it. The Bulgarian army counter-attacked but was repulsed. On 23 October the artillery fire of the Entente grew even more. The French were fighting near Kremenitsa. In the course of a week the Bulgarians tried to push them back without success but all Serbian attacks were also unsuccessful which led to massive casualties for both sides. Due to lack of munitions the Bulgarian artillery had to save shells which had a negative effect on the moral of the soldiers. On 7 November the enemy artillery started intense fire at 3/8 Brigade which occupied positions between Krape and Polog. After three days the losses of the brigade became so immense that on 10 November it abandoned its positions which were taken by the Serbs. On 19 November the Bulgarians also had to retreat from Bitola and took positions at 5 km to the north of the town. The front stabilized on the line Pelister - Hill 1248 - Hill 1050 - Dabica - Gradešnica.