After pushing back the Romanian forces manning the outposts, the enemy reached the main defensive line on the 21st of August, and in the early hours of the 22nd, launched its attack. After a powerful, one-hour artillery barrage, the Bulgarian infantry rushed forward towards the strongpoints. Each Romanian company was attacked 1 or 2 enemy regiments, but initially they managed to hold their positions against all the odds. Wave after wave of enemy infantrymen were mowed down by rifle and machine-gun fire, while the artillery fired everything it had at the attackers. But in the end, the sheer weight of numbers was too much, and the 79th Infantry Regiment, which had received the main blow, was forced to pull back, taking over 3000 casualties, after its supporting guns had run out of ammunition. The Supreme HQ rushed reinforcements to the area ( 15 battalions and 3 batteries ), but only a handful of units reached Turtucaia by the evening. At 17.00 hours the next day, a counterattack was launched using 4 fresh battalions under the cover of 3 batteries. The Romanian hit the enemy's right flank and gained some ground, but were soon stopped themselves. Everywhere else on the Turtucaia front, the line had held, but it soon had to be abandoned after the troops were in danger of being outflanked and encircled. During the night, Romanian troops retreated in order to the 2nd defense line, where the division's commander hoped to stop the enemy offensive. This meant that the remaining forces were crowded in a shrinking area, under heavy artillery fire. By the evening of the 24th, bitter fighting raged across the whole perimeter as the Romanian were slowly, but certainly being pushed back towards the Danube. That night, the Turtucaia bridgehead was finally abandoned, as it was clear that the 17th division couldn't possibly hold out any longer. Most of the troops retreated across the Danube, whilst the rest broke out of the pocket and headed for Silistra and the lines of the 9th division.

The loss of Turtucaia had an effect totally out of proportion at the highest levels of command. Though it was true that the 17th Division had indeed taken heavy casualties ( 10000 men killed, wounded and captured ) and that the city was lost, the Bulgarian 3rd Army had also lost some 9000 men, there was no serious danger that the Bulgarians might head for Bucharest or at least cross the Danube. Actually, the arrival of the Russian corps had balanced the situation and even created conditions for taking the initiative. Nevertheless, the Romanian Supreme HQ halted the offensive in Transilvania and rushed some of its units to Dobrogea, creating the Army of Dobrogea. Meanwhile, as the success of Turtucaia went to von Mackensen's head, on the 31st of August he ordered his army to re-deploy and engage the main Romanian and Russian forces to the north. Mackensen and his staff really believed that by applying pressure on the left flank, they could "throw the enemy into the Black Sea". This was nothing short of ridiculous, as by now the Bulgarian forces no longer had the numerical advantage and were evenly stretched across the front. The idea of the Bulgarian commander, general Toshev, of enveloping both flanks was no better, as it meant further spreading of its troops. Naturally, the Romanian and Russian divisions not only repulsed both attacks, but took the initiative and counterattacked, throwing back the Bulgarians. Two days later, another offensive, this time in the center ( 2 divisions supported by most of the heavy artillery ) was also halted, achieving only a 2-3 kilometers advance, in spite of the intervention of a newly-arrived Turkish division. By the 6th of September, the Romanian troops were ready to launch their own offensive, which they did, retaking all lost ground and inflicting heavy losses on the 4th Bulgarian division. A Serbian division, part of the Russian 24th Corps, distinguished itself during these actions. In the end, both sides halted the attacks and started to dig in. The first phase of the battle for Dobrogea was over.

After the 6th of September, the Romanian HQ had a serious problem : where should its forces be concentrated ? General Prezan, commander of the Northern Army thought the best thing to do was to stick to the original plan and resume the offensive in Transilvania, whilst reinforcing the Army of Dobrogea with units taken from the general reserve. On the other hand, the 3rd Romanian Army's new commanding officer, general Averescu believed that "We must stop the offensive in the north, reorganize the army quickly and launch with as many forces as possible a decisive action on the south front..". In the end, Averescu won the debate and was appointed commander-in-chief of the Army Group South, made up of the 3rd Army and the Army of Dobrogea. His new army group received three new divisions : the 21st and 22nd, taken from the 2nd Army and the 10th Division from the general reserve. Analyzing the situation, Averescu decided on a bold move : he would launch a frontal assault into Dobrogea and simultaneously cross the Danube into central Bulgaria with 6 divisions, falling behind the 3rd Bulgarian army. If the operation succeeded, most of the Central Powers's forces in Dobrogea would be encircled and destroyed within weeks. The Flamanda sector, 140 km away from the frontline was chosen as the crossing point. Five infantry divisions ( 10th, 16th, 18th, 21st and 22nd ) and a cavalry division were assigned for this mission.

Preparations began on the 4th of September, 1916. A 10 kilometer road was built from the nearest railway station right to the bank of the Danube to ensure the easy flow of men and materiel to the bridge. 5 artillery batteries whose fire was directed from a balloon were to protect the bridge against the possibility of an attack of the Austro-Hungarian fleet. Further up the Danube, mines were laid and a ship was sunk to block any enemy ships. The mine barrage was itself defended by two 150 mm artillery batteries and searchlights. 12 fighters and 2 anti-aircraft artillery batteries were supposed to protect the bridge from German planes and zeppelins. All these preparations were not completed until the 18th of September, yet von Mackensen and his staff were taken completely by surprise when the infantrymen of the 10th Division started to cross the Danube using small boats and ferries. Supported by the guns on the Romanian bank, they easily overran the few Bulgarian units in the area, and by the evening the towns of Silvopole and Brestov had been taken. The 21st Division also started to cross the Danube to aid their comrades. At 19.00 hours the bridge was completed and reinforcements were pouring across, widening the bridgehead, in spite of several German attempts to destroy the bridge from the air.

However, luck was not on Averescu's side. During the night, a powerful storm broke the bridge in two places, whilst the torential rain caused the Danube to flood the assembly area. By the early hours of the 19th, the bridge had been repaired thanks to the efforts of the engineers, but meanwhile, 3 Austrian monitors had managed to overcome the obstacles ( they could pass over the sunken ship thanks to the rising water level ) and at 9.30 they started shelling the bridge. Though they didn't actually score any direct hits, the flow of men and guns was seriously hampered and slowed down. In the end, hastily set up artillery pieces forced the Austrians to return to their base. On land however, things were going much better. The only enemy units in the area were 7 active battalions with 3 artillery batteries plus an improvised regiment made up of old men, half of which didn't even had a rifle! The Germans promised to rush the 217th German Infantry Division between the Romanian troops and Bulgaria's capital, Sofia, but since that unit was still forming up in the Bazargic area, it is unlikely that it could have arrived in time. Throughout the day, the two Romanian divisions expanded the bridgehead and fortified their positions. Things seemed to be going well, when suddendly, the Supreme HQ consulted Averescu and ordered to stop the operation. Only 2 regiments and the organic divisional artillery were to remain on the Bulgarian bank, and stick to the defense. The reason behind this apparently absurde was the start of another enemy offensive, this time on the north front, where the Romanian troops were being hard-pressed by the newly-arrived German 9th Army. Also, the Romanian "Army of Dobrogea"'s attack had been stopped with heavy losses. All divisions which were supposed to take part in the operation were again needed elsewhere. On the 20th, all forces returned to the Romanian bank of the Danube, thus ending the most daring Romanian offensive of 1916...