Battle of the Cerna Bend ( 1916 ) The Battle of the Cerna Bend ( ) , also referred to as the Battle of the Cerna Loop , was a two month long battle between the Bulgarian and Entente armies . The battle took place in the Macedonian Front during the First World War Allied Monastir Offensive in October and November 1916 . After extremely heavy fighting and severe casualties on both sides , the Bulgarians retreated from Bitola on the 19 November and took positions at 5 km to the north defeating all later attacks from there . However , the Entente entry in Bitola had no strategic value . The battle . 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 Cherna 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 Cherna 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 had to retreat from Bitola and took positions at 5 km to the north of the town on the line of Pelister from point 1248 to point 1050 . Aftermath . The Entente continued with their attempts for a breakthrough against the Bulgarians in the area of the River Cherna in the next year again without any success . The French attacks at point 1248 ( Battle of the Red Wall ) were defeat and the peak became known as the " Macedonian Shipka " ( referring to the famous battle of Shipka Pass ) . The Bulgarian army continued to hold the Macedonian Front against French , British , Serbian and Greek troops until the Franco - Serbian breakthrough at Dobro Pole on 15 September 1918 .