Despite the considerable numerical and material advantage of the attackers over the defenders, the Bulgarian and German defence of the positions in the loop of the river Crna remained a formidable obstacle, which the Allies were unable to defeat not only in 1917 but until the end of the war.

The three-month-long Monastir Offensive provided the Allies with only limited tactical successes, but it failed to knock Bulgaria out of the war by a combined attack of General Sarrail's forces and the Romanian Army.

On the tactical level, the front line was moved in favour of the Allies by only about 50 km in the Sector of General Winkler's 11th German-Bulgarian Army.

However, by the end of November, the Bulgarians and Germans were able to firmly establish themselves on the Chervena Stena – height 1248 – Hill 1050 – Dabica – Gradešnica defensive line and subsequently repel all Allied attempts to dislodge them of their positions.

The strategic situation in the early spring of 1917 on all European theatres of war, except the Romanian portion of the Eastern Front, favoured implementing the Allied offensive plans adopted during the inter-allied conference of November 1916, held in Chantilly, France.

[7] In the Crna Bend sector, the planned attack was assigned to the left-right of the French Army of the East – the so-called First Group of Divisions(under the command of General Georges Lebouc) and the Italian Expeditionary Force.

The Allied artillery on this part of the front was forced to pause its barrage for some time in the afternoon due to the appearance of German fighter aircraft and the destruction of one of their observation balloons.

[15] With the coming of the night, the Allied fire was significantly reduced in intensity, which gave a chance to the defenders to repair part of the inflicted damage.

On this day, the Central Powers' artillery took a more active part in the battle and often engaged in counter-infantry and counter-battery work with the help of German reconnaissance planes.

[17] While the Bulgarian infantry units suffered 945 casualties during the four days of bombardment, the losses of the artillery were only ten men killed or wounded and several guns damaged or destroyed.

As the infantry prepared, the artillery resumed its barrage with much greater vigour, engulfing the entire defensive line in a cloud of smoke and dust again.

To the right, parts of the 61st regiment took advantage of the dust cloud left by the barrage, capturing a forward trench that the Bulgarians had evacuated to preserve their infantry from the Allied artillery fire.

Soon after, the Bulgarian and German rifle, machine gun and artillery fire intensified and caused heavy casualties to the attackers as it hit the Italians from their front and flanks.

The Germans and Bulgarians quickly regained control of their lost trenches(capturing 120 prisoners in the process), forcing the Italian 61st Regiment to fall back to its starting positions.

[22][23] In the center of the Italian front of attack, the 161st Infantry Regiment was tasked with taking Hill 1050, but its advance met with a powerful barrage delivered by the Bulgarian artillery.

[22][23] While they advanced these troops were also subjected to very heavy artillery, trench-mortar and machine-gun fire which was the prelude for a counterattack delivered by the German Guard Jaegers that saw the entire Italian regiment thrown back to its original positions.

It attacked a hill defended by troops of the German 45th Infantry Regiment and initially succeeded in overcoming the barbed wire and occupying part of the first line of trenches.

[22][23] To their right, however, the 16th French Colonial Division failed to permanently capture the vital hill Piton Rocheaux, which left the Italian flank unsupported and vulnerable.

The Allied bombardment destroyed many of the Bulgarian forward infantry observation posts, caused damage to the fortifications and covered the three hills that were the attack's objectives in a dense cloud of smoke and dust.

To the right, the French 37th Colonial Regiment had better luck and managed to enter and occupy the trenches on Hill "Vaskova Visochina"(Tranchees rouges) undetected, where they placed in position several machine guns.

The Bulgarian battalion's troops, responsible for defending the hill, immediately came out of their shelters and counterattacked under a hail of rifle and machine gun bullets.

As more Bulgarian infantry and German machine guns became involved in the counterattack, the 37th Colonial Regiment's soldiers were finally forced to abandon the hill and retreat.

The artillery preparation in this sector began at 5:15 in the morning(guided by an observation balloon), reaching peak intensity at about 6:00 when it covered most of the German and Bulgarian lines.

The French failed to take the vital position named "Caesar," giving a tactical advantage to the defenders who could concentrate their efforts on deflecting the Russian attack.

At Dabica, however, the German artillery proved too weak to halt the attack of the Russian 4th Infantry Regiment, whose troops successfully penetrated the main trench with the help of hand grenades and advanced so rapidly through it that by 8:00 the entire hill fell under their control.

[20][31] As a result, the headquarters of the 22nd German-Bulgarian lost connection with its troops in the area, receiving no clear information about the situation until late in the afternoon.

At 14:40, the commander of the Franco-Russian forces, General Lebouc, ordered the Russian Brigade to attack and capture "Heintselman" with its 3rd regiment as the 17th Colonial Division carried out a new assault against "Caesar.

The commander of the 22nd Infantry Brigade colonel von Reuter planned to retake his lost positions by attacking from both the west and east sides of "Dabica."

With the recapture of "Dabica," the integrity of the entire defensive line in the Crna Bend sector was restored, and the battle on 9 May ended in a decisive victory for the Central Powers.

[25] Despite the failure, General Sarrail was not ready to give up on his offensive and new attacks were made by the Italians and French in the Crna Bend on 11 and 17 May, which failed.