According to the Operational Directive no. 1 and to the orders of High General Staff, No. 2766 and 2767 from 13 August 1916, at 15 August the forces of the Second Army launched the offensive, starting from the land strip between the Slanicului Valley and the Piatra Craiului Mountains. In the moment when the military operations started, the Second Army (commanded by the general Alexandru Averescu) consisted of the 2nd Army Corps (3rd and 4th infantry divisions), 3rd Army Corps (5th and 6th Infantry Divisions), 1st Cavalry Division and other units, subunits, special formations and services. The offensive of the Second Army was supported from the right flank by the “Oituz” Group, belonging to the “North” Army. The “Olt-Lotru” Group, belonging to the First Army, supported the left flank.
The combat disposition of the Second Army was the following: the 3rd Army Corps between Vrancea Mountains and Baiul Mountains, the 2nd Army Corps from Baiul Mountains to the Fagaras massifs, and the 1st Cavalry Division was in reserve, in the Curtea de Arges area. The Second Army consisted of 78 infantry battalions, 71 artillery batteries and 12 cavalry squadrons.
Facing the direction of attack of the Romanian Second Army was the 71st Austro-Hungarian Infantry Division (commanded by the general Anton von Goldbach), with 9 infantry battalions, 8 artillery batteries and 1 cavalry squadron.
During the first stage (15 – 20 August), the Romanian divisions advanced along the following directions:
The “Putna” Group (5 battalions, 2 batteries) from the 6th Infantry Division penetrated into the Lepsa, Putna, Naruja and Zabala valleys, and at 16th of August, after it crossed over the Vrancea Mountains, it penetrated into the Tirgul Secuiesc depression, reaching the Ghelnita – Zabala alignment, succeeding the junction with the “Oituz” Group, which reached the line at Ghelnita, Targul Secuiesc.
The “Buzau” Group (7 battalions, 6 batteries) from the 6th Infantry Division advanced along the Basca Mica (“The Small Basca”), Basca Mare (“The Big Basca”) and Buzau valleys. They repelled the 43rd Austrian Regiment at Covasna and reached Borosneul Mare (“The Big Borosneu”) – Dobarlau – Teliu alignment.
The “Tabla Butii” Group (3 battalions) from the 5th Infantry Division conquered Vama Buzaului, were the enemy mounted a strong resistance. The enemy losses were 132 dead and wounded, and 492 prisoners.
The “Bratocea” Group (6 battalions, 6 batteries) repulsed the enemy in the Teleajen Valley and in cooperation with the “Predelus” Group (3 battalions, one battery) entered in the Brasov depression, were on 17th of August they reached the Zizin, Carpinis, Sacele alignment. Both groups were parts of the 5th Infantry Division.
The 4th Infantry Division with the “Predeal” Group (9 battalions, 9 batteries) penetrated during the night of 14-15 August in the Predeal custom house, and annihilated the frontier guard pickets from Susai, Timis and the Rasnov Valley. After heavy fights in the narrow path between the massifs of Piatra Mare (“The Big Stone”) and Postavarul, at 16th of August the troops of the 6th regiment “Mihai Viteazul” (“Mihai the Brave”) entered in the Brasov city. During the period of 16 – 20 August, the 4th Infantry Division maintained the Predeal gorge, and on 20th of August conquered the Feldioara and Vlasceni villages, repulsing the enemy beyond the Olt River.
The “Bran” Group (9 battalions, 5 batteries), consisting of the Regiments 30 “Muscel” and 22 “Dambovita”, belonging to the 4th Infantry Division. They crossed over the Rucar-Bran mountain pass and conquered Giuvala mountain pass and the heights of Bran, Magura and Dealul Cetatii (“Fortress Hill”). On August 18 the villages Tohanu Vechi (“The Old Tohan”), Tohanu Nou (“The New Tohan”) and Zarnesti were conquered. On 20th of August the 4th Infantry Division reached the Halchiu, Vladeni alignment. The “Moroeni” Group (2 battalions, one battery) assured the link between the “Bran” and “Putna” groups.
At the end of the first stage of the operations, the Second Army was on the following line: Catalina (south of Targu Secuiesc) – Zabala – Dobarlau – Prejmer – Feldioara – Vladeni.
In the second stage of the offensive operation (21 – 28 August 1916) the goal was to reach the alignment Baraolt – Racos – right shore of Olt River, and to concentrate the main forces in the area: Covasna, Sf. Gheorghe, Feldioara, Vladeni, Brasov.
At 24th of August the 5th Division was taken from the Second Army and sent to the front in Dobrogea. In its place was brought the 22nd Infantry Division.
The 6th Infantry Division restarted its advance at 24th of August and in the same day it conquered the Sf. Gheorghe city.
The 3rd Division advanced and reached the Sercaia – Sinca Veche line, repulsing the enemy positioned on the southern peaks of the Persani Mountains.
At 26th of August the general Grigore Crainiceanu was appointed commander of the Second Army. General Averescu was appointed commander of the Army Group “South”, intended to be used at Flamanda.
At the end of the second stage, the Second Army controlled the whole Brasov depression, having all its units at north of Carpatii Meridionali (“the Southern Carpathians”), with the exception of the First Cavalry Division. The enemy was repulsed beyond the Persani Mountains and the Olt River, and the Second Army reached the line Catalina – Arcus – Valcele – Feldioara – Sercaia – Sinca Veche.
In the third stage of the offensive operation (29th of August – 13th of September 1916) the goal was to take the Olt and Homorod valleys, between meresti and Fagaras. After reorganizing the grand units, which lasted until the September 1st, the offensive restarted as following:
The 3rd Army Corps, with the 6th and 22nd Infantry Divisions and the 3rd Brigade “Calarasi”, started their offensive between Racosul de Sus (“the Upper Racos”) and Rupea (on the northern shore of the Olt River). The 3rd Brigade “Calarasi” took the enemy positions at Meresti. The 6th Infantry Division advanced in the area between Olt and Homorodul Mic (“the Small Homorod”), penetrating at September 3rd in the Homorodul Mic valley, between Meresti and Mercheasa. The 22nd Infantry Division forced the crossing of Olt at Rupea, liberated the locality and reached the heights at north-west of Rupea, where it remained until the 4th of September.
The 2nd Army Corps, with the 3rd and 4th Infantry Divisions and the 2nd Brigade “Calarasi”, started their offensive in the area Crihalma, Fagaras. The 3rd Infantry Division forced the crossing of Olt at Crihalma, Venetia de Jos (“the Lower Venetia”) and Halmeag, and obtained a bridgehead by conquering the Daisoara locality. Here the Romanian troops benefited from the support of the local people. A young woman from Parau village guided a Romanian subunit in the rear of enemy positions. At Voila, the attempt of the 2nd Brigade “Calarasi” to force the crossing of Olt was unsuccessful. This unit regrouped at Margineni and it was later replaced by the 4th Infantry Division.
At 5th of September the 21st and 22nd Infantry Divisions were taken from their subordination to the Second Army to be sent to the southern front. The Second Army remained with 3 infantry divisions (the 3rd, the 4th, the 6th) and 2 cavalry brigades (the 2nd and the 3rd), on an alignment almost 300 km in length. In the same time the enemy was strengthen with new units (the 19th Brigade-Landsturm, the 1st Austro-Hungarian Cavalry Division), which together with the 71st Infantry Division started to resist in a better and better organized manner. Under these conditions, at 6th of September the Second Army got the order to operate in defensive, along the alignment they reached:
Odorheiul Secuiesc – Palos – Fiser – Daisoara – Ticusu Nou – Toarcla – Sasaus – Nou Roman – Cartisoara – Avrig.
At 7th of September the Second Army received the order to fortify 3 echelon lines: first on the already reached alignment, second at northern entrance of the Brasov and Fagaras passes, and the third was the alignment as it was before the offensive started. Each echelon was supposed to consist from few fortified lines. During the 6 – 13 September period the Second Army organized its defense, in the same time with the first attempts of the enemy to break through the Romanian lines.
During the 29 days of the operation, the Second Army succeeded an advance through the enemy lines 120 km in depth, in the right wing (between Vrancea Mountains and Ticusu Nou locality). The advance was 90 km in depth in the left wing (between Bran and Avrig). At the end of the operation, the front of Second Army stretched for about 100 km, between Odorheiul Secuiesc and Avrig.