After retaking Northern Bukovina, the Romanian 3rd Army was subordinated to the German 11th Army. It was made up of the Cavalry Corps (5th, 6th and 8th Cavalry Brigades, the Romanian semi-motorized cavalry units), the Mountain Corps (1st, 2nd and 4th Mountain Brigades), a field artillery regiment (of the 7th Infantry Division), the 52nd and 57th Motorized Heavy Artillery Battalions and the 54th AT Company. Also, the 19th and 21st Observation Squadrons and 111th Liason Squadron were assigned to it. There were in total 74,700 men, under the command of. lt. gen. Petre Dumitrescu.

On the eastern bank of the Dnestr River were the forces of the 18th Soviet Army, including the 130th and 164th Rifle Divisions and machine-gun battalions of the 12th Soviet Fortified District. These forces were deployed in an echeloned fortification system with over 150 pillboxes.

On 17 July 1941, the 3rd Army began to cross the river early in the morning, by surprise, with the 1st and 4th Mountain Brigades and the 6th and 10th Motorized [I]Rosiori[/I] Regiments (Colonel Mainescu Detachment), later backed by the 3rd Motorized [I]Calarasi[/I] Regiment. Having reached the opposite bank, the assault groups attacked the pillboxes with explosives and direct fire from machine-guns, small caliber AT and mountain guns. By noon the first line of fortifications was taken. The Romanian units had successfully established several bridgeheads and then resumed the advance northwards. At 1700 hours, the Soviets launched a first counterattack in the left flank of the 3rd Army with the 164th Rifle Division supported by tanks. The battalions of the 1st Mountain Brigade, which were already up to 1 km south of Honkovty, were the ones which received the main shock. The counterattack was repulsed but a second, much stronger one, carried out at 1930 hours, pushed the battalions from the left flank of the 1st Brigade roughly 1.5 km back. In the area of operations of the Cavalry Corps, the 6th and 10th [I]Rosiori[/I] Regiments have accomplished their mission by destroying the pillboxes and occupying Liasevty. By the end of the day they have established a line goin from East of Lencauti to South of Leadova. The next day, the Red Army made great efforts to liquidate the bridgehead, starting the counterattacks at 0530 hours against the 4th Mountain Brigade. These were carried out by troops of the 130th and 164th Rifle Divisions, assisted by tanks and artillery. By afternoon the pressure increased and with a final effort the Soviet forces managed to penetrate between the two mountain brigades, only to be stopped at Hill 245 by the stiff resistance of the 9th Mountain Group. This was done, however, at the cost of heavy losses, including the mountain group commander, two battalion commanders and a mountain artillery battalion commander. The 1st Mountain Brigade, situated in the flank of enemy forces, delivered a blow towards Honkovty with four battalions supported by most of the artillery, including the 52nd and 57th Motorized Heavy Artillery Battalions, repulsing the enemy to the North and taking the village. The resistance of the 9th Mountain Group and the attack of the 1st Mountain Brigade saved the situation of the troops in the bridgehead. During 19 July the Soviet resistance was weak and the 1st and the 4th Mountain Brigades resumed the advance northwards, while the Cavalry Corps took Serebria and maneuvered around the last strongpoints of the Stalin Line. The losses suffered by the 3rd Army during the three days of battle were 1,892 (666 dead and 1,226 wounded). Over 1,000 Soviet soldiers were captured along with a large amount of equipment and 182 pillboxes and bunkers were destroyed.

The 3rd Army was then placed between the 11th and 17th German Army. The Cavalry Corps organized the Mechanized Detachment "Col. Radu Korne" (motorized cavalry, artillery and pioneers). Its mission was to follow closely the retreating Soviet forces. The rest of the 3rd Army had to help in eliminating the remains of the Soviet 12th Army, encircled near Uman by German forces.

On 10 August the Romanian troops had reached the river Bug. They replaced the Hungarian Rapid Corps in the bridgehead at Voznezensk. Here there were heavy fights near Adamkova, Marianovka and Vladimirovka with Soviet troops trying to strike the German 11th Army's flank. Then, on 19 August, the 3rd Army advanced towards Krivoyrog. The Cavalry Corps had captured 12,783 soldiers, 450 vehicles and 70 tanks.

Between 1 and 14 September, the 3rd Army occupied a defensive position on the German 30th Corps' flank, which was forcing the river Dnepr. It had to face powerful counterattacks from the 18th Soviet Army near Sablukovka, Kat Sarovka, Anastasievka and Mikhailovka. During the offensive from the Dnestr to the Dnepr, the 3rd Army had suffered 19,861 casualties (6,786 dead, 12,942 wounded and 133 missing).

On 19 September Army Group South ordered the Romanian troops to force the Dnepr. By 25 September, the 3rd Army and the German 30th Corps were occupying a defensive position in the Nogay Steppe, North of Sea of Azov, to secure the flank of the German 11th Army that was trying to advance in the Crimean Peninsula. The Mountain Corps had its left flank on the Dnepr and the Cavalry Corps had its right flank on the seaside. Between them, there was the German 30th Corps (2 divisions).

On 24 September, 12 Soviet divisions from the 9th and 18th Army, supported by tanks, airplanes and artillery, launched a devastating assault on the positions of the 3rd Army and of the 30th Corps. Their goal was to ease the pressure on the Soviet 51st Army, which was isolated in Crimea. The front was broken in the sectors of the 2nd and 4th Romanian Mountain Brigades and 5th and 6th Romanian Cavalry Brigades. Also the 170th German Infantry Division and 8th Romanian Cavalry Brigade were pushed back. The situation was almost desperate. However, there were still many pockets of resistance that were holding out and slowing down the Soviet advance. The Romanian and German forces suffered heavy casualties (up to 50% in some cases) in the fights at Balky, Vladimirovka, Ulyanovka and Akymovka. On 29 September the German 11th Army dispatched the 49th Mountain Corps and from the North attacked the German 1st Panzer Group. Still the situation was critical. Only with the arrival of the "Leibstandarte Adolf Hitler" SS Division things got better. Its attack, together with the Romanian Cavalry Corps, reestablished the situation. On 3 October the last Soviet assaults were repulsed. From this date on the Romanian 3rd Army and the German 1st Panzer Group and 11th Army continued their offensive actions: the Panzer Group in north, the Romanian Mountain Corps and German 49th Mountain Corps in center and the Romanian Cavalry Corps and the "Leibstandarte Adolf Hitler" SS Division in south (by the seaside). The Cavalry Corps made rapid advancement and, on 7 October, met up with the German 16th Armored Division, encircling the Soviet 9th and 18th Army. The 3rd Army took 6,700 prisoners.

After this operation, the 3rd Army returned under the direct command of the Romanian General Headquarters and remained in defensive positions on the seaside (to prevent a Soviet landings behind German lines). But some of its units continued to fight on the front. At the request of gen. Erich von Manstein, the CO of the German 11th Army, the Mechanized Detachment "Col. Radu Korne" (6th and 10th Motorized Rosiori Regiments, an AT battalion, the 54th Motorized Heavy Artillery Battalion and a motorcycle company) was assigned to his command. A short time after that, the Mountain Corps (1st Mountain Brigade, 8th Cavalry Brigade and 19th Artillery Regiment) was joined it.

The 11th Army started the offensive in the Perekop sector on 19 October. The Mountain Corps, however, conducted only an active defense. In the evening of 28 October, when the resistance in the Perekop Isthmus had been defeated, it finally received the order to advance. The 1st Mountain Brigade was going to attack through the Salkovo Isthmus, while the 8th Cavalry Brigade was suppose to take Genichesk. The assault started on 29 October. The Salkovo front was only 2 km wide, which permitted an attack with two battalions, and was very heavily fortified. In his memoirs, von Manstein refered to the Salkovo Isthmus as “useless for an attack”. In the first day, the [i]vanatori de munte[/i] (mountain troops) managed to advance only about 1.5 km, despite having artillery and air support (several Stukas from StG 77 bombed Soviet positions). The cavalry didn’t have too much success either at Genichesk. However, the German forces, which were advancing through the Perekop Isthmus into Crimea, were threatening to cut of the Soviet troops in the Salkovo Isthmus. So the next day they started to fall back. The 1st Mountain Brigade engaged the rear-guard and passed through the last line of fortifications by noon and then pursued the retreating Soviets to the Sivash Sea. But they managed to escape and blow up the bridges that connected the Salkovo Isthmus with Crimea. About 250 prisoners were taken. On 31 October the 1st Mountain Brigade started to cross over in boats and, later that day, on a pontoon bridge built by German engineers. Since the 8th Cavalry Brigade didn’t have too much success at Genichesk and its mobility was more suited for the pursuing actions in Crimea, it was decided to contain the Soviet forces with the 4th [i]Rosiori[/i] Regiment. The 2nd Cavalry Regiment and the 3rd Motorized Cavalry Regiment were sent through the cleared Salkovo Isthmus to Crimea and subordinated to the German 42nd Corps.

The Korne Motorized Detachment entered in Crimea through the Perekop Isthmus and made a quick advance and intercepted the Simferopol-Yevpatoria highway on 31 October, cutting off the retreat route towards Sevastopol.

The 1st Mountain Brigade was given the task to clear up the Yaila Mountains. For this it was split up into three detachments. On 5 November3 they reached the Black Sea near Sudak, after marching and fighting along 180 km in four days and taking 2,247 prisoners. A notable action was the one of the 58th Recon Group (a machine-gun squadron and two cavalry platoons). It was assigned to the 1st Mountain Brigade. The Group was part of the vanguard. In the morning of 5 November, it reached the B. Yantura forest and was received with powerful MG fire. They maneuvered to the north and captured 2 officers and 41 soldiers. Then they continued the advance towards Tuak and managed to surprise about 150 Soviets at the western exit of the town. These were captured without a fight, after one cavalry platoon infiltrated behind them and made them surrender.

But the big “pot” came the next day. Their mission was to clear the road to Kuruusen of any enemy groups. They found, however, an entire Soviet cavalry regiment. It was lined up in a column without any precautions. The two cavalry platoons quickly rode on each side of the road, firing at the Soviets and managing to surprise them. They threw down their weapons and surrendered. 1,210 POWs were taken and an enormous quantity of weapons.

The 8th Cavalry Brigade was temporarily under the command of the German 42nd Corps. It started its pursuit on 3 November and was permanently in the front line. By 9 November it was in the Kerch Peninsula with the rest of the German 42nd Corps. Between 10-12 the 8th Cavalry Brigade was assigned the task of cleaning up the seaside of the Soviet troops that remained. After that date it returned under the command of the Mountain Corps. It had fought across 240 km and taken about 1,300 prisoners.

On 10 November, the 11th Army started to prepare the assault on Sevastopol. This mission was assigned to the German 54th and 30th Corps. The Romanian Mountain Corps was assigned to the defense of the Crimean coast between Sudak and Alushta. A new Romanian unit, the 4th Mountain Brigade, was sent to Crimea at the request of the German command. It arrived at its destination on 26 November and on 2 December commenced the anti-partisan actions in the Yaila Mountains. These proved to be quite a problem. The 1st Mountain Brigade also fought them between 6 and 18 November, before it was sent to take part in the assault on Sevastopol, but did not manage to wipe them out. However, by 15 December, the 4th Mountain Brigade managed secure most of communication routes and to destroy the partisan nests, despite the terrible winter conditions (-25C, blizzard).

As already mentioned, on 18 November the 1st Mountain Brigade received the order to move to Sevastopol were it was going to be subordinated to the German 30th Corps, in the southern part of the Sevastopol front. It arrived in the designated area on 22. Immediately the 1st Mountain Group was assigned to the 72nd Infantry Division. After two days it was reinforced with the 14th Battalion, a mountain artillery battalion and the 4th Artillery Regiment. The rest of the brigade was assigned to the defense of the coast line and to anti-partisan duties.

On 23 November 1941, the 1st Mountain Group (2nd and 3rd Battalion) with the 2nd Mountain Pioneer Battalion, the 37th AT Company and the 4th Artillery Regiment replace the German 124th Regiment on the front line. On 25 November the 1st Mountain Group took the Alsu village and two days later it assaulted the Denkmal Heights, but failed to take it completely because of the fierce Soviet resistance and the bad weather. The “Lt. Col. Dinculescu” Group (23rd and 24th Battalion) replaced the 1st Group on 6 December and was submitted to several Soviet attacks between 8-13 December, but repulsed all of them.

The assault was planned for 17 December. The 1st Mountain Brigade’s objective was the Chapel Hill. The attack was supposed to start at 6:55 with the two groups simultaneously, each with a battalion. Because of some mistakes in the communication of the orders, the 3rd Mountain Battalion didn’t reach the starting position at the time when it was suppose to and the assault was carried out only by the 23rd Battalion (Dinculescu Group). The advance was stopped by the Soviets on the Karlovka stream. Later that day a second assault was launched, this time with together with the 2nd Battalion, but failed, mainly because of the Red Army troops in the Karlovka village which were firing in the Romanian flank. It was obvious that the village needed to be taken before any further advance could be made. So the next day was used for intense preparations. The Soviets, however, attacked the positions of the 2nd and 23rd Battalion, which suffered heavy casualties, mostly because of the intense mortar shelling. Maj. Gheorghe Stancu, the commander of the 2nd Battalion, was killed that day when his command post was hit by a mortar shell. The assault on 19 December commenced at 7:00. The 3rd Battalion managed to take the northern part of the Karlovka village within an hour. The 2nd Battalion attacked from the south, but stopped in front of the Soviet pillboxes. However, with the support of Stukas from StG 77, which launched their bombs with excellent precision this obstacle was surmounted and the village was taken, after some very violent fighting, even hand-to-hand. In the meanwhile the 1st Battalion continued the advance towards the Chapel Hill. The “Dinculescu” Group was subordinated to the German 105th Infantry Regiment and fought that day under its orders. The command point was hit by a heavy mortar shell and lt. col. Gheorghe Dinculescu was killed. During the next days, the offensive actions continued to take the Chorgun village and the heights east and west of it. On 20, the village and the eastern hills were secured, but the Soviet resistance was very powerful in the western part. The guns had to be brought close in order to fire directly on the pillboxes. Several AT pieces were carried up the hills east of Chogun with enormous effort and the obstacle was destroyed. Thus on 23 December, the 1st Mountain Brigade and the 170th Infantry Division took the Chapel Hill. During the 7 day offensive (17-23 December) the brigade lost 1,261 men (331 dead, 801 wounded, 129 missing). But the brigade and its commander (maj. gen. Mihail Lascar) won the admiration of Gen. von Manstein, who mentions him in his memoirs, but during the second Battle of Sevastopol, when Lascar was no longer the commanding officer of the 1st Mountain Brigade.

Another Romanian unit that took part in the first battle of Sevastopol was the “Korne” Detachment, which was subordinated to the 54th Corps in the northern part of the Sevastopol front. It was situated on the extreme right of the corps and attacked parallel with the seaside towards the Kacha Valley, securing the flank of the German 22nd Infantry Division, which was the main offensive element of the 54th Corps. It reached the valley on 23 December and by 25 it had already cleared the area of Soviet troops.