The 'Bucharest-Arad Offensive Operation', also known as the 'Romanian Offensive Operation', was a major Soviet and Romanian undertaking to take northern Romania from German, Hungarian and anti-communist Romanian forces (30 August/3 October 1944).

The German defeat in the '2^nd Iassy-Kishinev Strategic Offensive Operation' and the success of the August Uprising in Romania created conditions favourable for the subsequent Soviet offensive to the south-west across the northern part of Romania. The German-led forces' continuous front was ripped apart over a large area and led to a retreat on several axes: part of the German forces attempted to escape into Bulgaria and Yugoslavia, and part to the Carpathian mountain area and Hungary. A wide operational void lay open in front of the Soviet forces, and the Soviet supreme command sought to exploit this unique opportunity.

On 23 August, King Mihai I of Romania led a coup d'état against Mareșal al Romania Ion Antonescu, the Conducător of Romania, and the new government surrendered to the Allies and declared war on Germany.

In Romania itself, there was a powerful upsurge of anti-fascist patriotic sentiment but, quite contrary to the expectations of many Soviet leaders, the Romanian army as a whole strongly favoured a switch of allegiance from Germany to the USSR, though many officers still wished to retain their association with the Germans and thus either deserted or fled to rejoin the Germans; there were also several suicides in the officer corps as a result of this dichotomy of loyalty. Conversely, many Romanian enlisted or conscripted soldiers used their own initiative to provided assistance to the Soviet troops or to join forces with them. However, the king’s supporters and the Romanian high command sought to evade active operations against the Germans and to provide them with the opportunity for a peaceful departure from Romania. Moreover, the new Romanian government of Constantin Sănătescu made every effort to persuade the Western Allies to move US and British troops to Bucharest.

On 26 August, the government of Bulgaria, to the south of Romania, announced this nation’s complete neutrality, which precluded the active commitment of Bulgarian troops to fight alongside those of Germany. Three days later, the spate of military defeats suffered by the Axis forces led to a government crisis in Hungary and the start of the Slovak national uprising in German-occupied Czechoslovakia.

As this time, the southern wing of Generaloberst Johannes Friessner’s Heeresgruppe 'Südukraine' had ceased to exist as an effective force, its remnants being scattered formations and units which fled to Bulgaria, and the northern wing controlled no more than six divisions, some of which had already been severely degraded by their significant losses, and up to 300 aircraft. In Transylvania there were eight Hungarian divisions and brigades, as well as 30 border battalions. Within Hungary itself, there were another eight Hungarian divisions and brigades, out of which Altábornagy Jenö Major’s Hungarian 2^nd Army was being hastily formed, and troops which could be transferred to Romania from the central part of the Carpathian mountains, where Altábornagy László Dezsöo’s Hungarian 1^st Army was defending. From the forces in Greece and the Balkans controlled by Generalfeldmarschall Maximilian Reichsfreiherr von Weichs’s Heeresgruppe 'F' and Generaloberst Alexander Löhr’s Heeresgruppe 'D', the Germans could transfer several divisions to Romania (such a transfer was speedily put in hand), but in the current situation all this took time which the Germans did not have. It would be possible to stop the Soviet forces only after a continuous front had been re-established, and in the meantime the Germans could only hope to exploit the favourable terrain conditions in the southern part of the Carpathian mountains, where all the mountain passes had to be seized.

On the other hand, on the border with Transylvania there were 20 Romanian divisions of General de corp de armatâ Nicolae Macici’s 1^st Army and General de divizie Gheorghe Avramescu’s 4^th Army, which the new Romanian government ordered to disarm all German formations and units which did not leave Romania and oppose any German and/or Hungarian forces which entered the country. These rear-area rear armies comprised mainly inexperienced recruits and older soldiers, however, and were also very weakly armed and had practically no tanks.

Given this overall situation, the Soviet supreme command on 29 August ordered General (from 12 September Marshal Sovetskogo Soyuza) Fyedor I. Tolbukhin to commit his 3^rd Ukrainian Front to the occupation of the Romanian/Bulgarian frontier region and prepare for the start of hostilities against Bulgaria.

General (from 10 September Marshal Sovetskogo Soyuza) Rodion Ya. Malinovsky was ordered to commit part of his 2^nd Ukrainian Front, on the right of the 3^rd Ukrainian Front, in the form of General Polkovnik Sergei G. Trofimenko’s 27^th Army, General Polkovnik Ivan M. Managarov’s 53^rd Army and General Polkovnik Andrei G. Kravchenko’s 6^th Tank Army, in an undertaking to bypass the southern part of the Carpathian mountains and advance up the plain of the Danube river to the border with Hungary and Yugoslavia in the area to the west of Giurgiu, then advance in the general direction of Slatin and Turnu Severin by 7 or 8 September, and take these cities. The 3^rd Ukrainian Front’s right wing (General Polkovnik Mikhail S. Shumilov’s 7^th Guards Army and General Leytenant Filipp F. Zhmachenko’s 40^th Army) was to advance on Satu Mare, bypassing the Carpathian mountains from the east. By the start of the operation, the 2^nd Ukrainian Front had 681,556. In front of the 2^nd Ukrainian Front’s right flank, the previously solid German front had collapsed, but in front of the same front’s left wing and partially in front of its centre, a stable defence had been preserved on the basis of the convenient mountainous and wooded area of ​​the Carpathian mountains.

The Germans intended to restore a continuous front between Heeresgruppe 'Südukraine' and Heeresgruppe 'F' along the eastern and southern parts of the Carpathian mountains and the western part of the Balkans. For this , the Hungarian 2^nd Army was ordered to begin, at a date no later than 5 September, an offensive from the area of Cluj and Turda to the south with the aim of capturing the passes through the southern part of the Carpathian mountains.

Taking full advantage of the favourable political and military situation, on 30 August, the day following the completion of the '2^nd Iassy-Kishinev Strategic Offensive Operation', the 2^nd Ukrainian Front began its new offensive to the south-west. On 31 August, the vanguard of the Soviet forces entered Bucharest without a fight, but was almost immediately withdrawn for political reasons. Pursuing broken and scattered German formations and units, by 5 September, the main Soviet forces reached the line between Kampulung and Zimnich via Pitesti and Karakal after an advance of between 50 and 85 miles (80 and 140 km), and the advance elements of the 6^th Tank Army reached the Danube river on the border of Yugoslavia near Turnu Severin. On the 2^nd Ukrainian Front’s right wing, during this same period the 40^th Army and 7^th Guards Army advanced only some 9.33 to 12.5 miles (15 to 20 km), but broke through the defences which had been created on their axes of advance and in which the Germans put up a stiff resistance.

Acting on German instructions, on the morning of 5 September the Hungarian 2^nd Army (six Hungarian and German divisions) attacked the forward units of the Romanian 4^th Army from the Turda region and in two days moved some 12.5 to 18.5 miles (20 to 30 km) to the south, and in the following days as much as 30 miles (50 km). The Hungarian army’s task was to seize the passes through the southern part of the Carpathian mountains and hold them in the face of the Soviet advance. The main strength of the Romanian 4^th Army was located primarily to the south, leaving northern and central Romania under threat of occupation by Soviet forces.

To reduce the possibility of operational disunity in the Soviet and Romanian forces, on 6 September operational control of the Romanian 1^st Army and Romanian 4^th Army was passed to the 2^nd Ukrainian Front, as too was command of Romanian I Corps and Romanian VI Corps (more than 138,000 men and 580 pieces of artillery) and the Romanian I Air Corps (113 serviceable aircraft).

While the first phase of the 'Bucharest-Arad Offensive Offensive Operation; had been aligned largely to the west, the second phase saw a shift in this alignment to the north. Thus, on 6 September, Malinovsky ordered Kravchenko’s 6^th Tank Army to turn sharply to the north and by 12 September to take the area of Dezh, Cluj and Shermeshel; the 27^th Army received essentially the same order, and the 53^rd Army was to turn to the north-west and occupy the line between Brad and Lugozh. These tasks were swiftly achieved: by the evening of 11 September, the 6^th Tank Army had swept forward rapidly over a march of 155 miles (250 km) to reach the position being held by the Romanian 4^th Army. With no operational pause, the Soviet and Romanian troops launched an offensive here and by 13 September had driven the Hungarian 2^nd Army back to its original position, and had occupied Cluj on 12 September. By the end of 15 September, the Soviet 27^th Army and Romanian 4^th Army had reached the line between Targu-Mures and Turda, but the fighting in this area assumed a protracted nature. To the west, the 53^rd Army advanced some 135 miles (220 km) in seven days and occupied the Caransebes region. In the eastern part of the Carpathian mountains, the 40^th Army and 7^th Guards Army in these same days were able to break the German resistance, accelerated the pace of their offensive and advanced up to 80 miles (130 km). Throughout the period, combat continued as the Soviet forces destroyed scattered groups of German troops trying to break out of the encirclement near Iassy.

In general, by 15 September the 2^nd Ukrainian Front had almost completely reached the Romanian/Hungarian border established by the Vienna Arbitration of 1940. By that time, the Germans had managed to create a new front line along the frontier, on which there were 27 German and Hungarian divisions and brigades, including six Panzer and Panzergrenadier divisions. Moreover, on this day General Maximilian Fretter-Pico’s German 6^th Army and Vezérezredes József Heszlényi’s Hungarian 3^rd Army launched a new attempt to counterattack toward Arad and Timişoara in order to halt the advance of the 2^nd Ukrainian Front’s left wing in the central Danube river’s lowlands. In three days, the Germans and Hungarians pushed back elements of the Macici’s Romanian 1^st Army by between 18.5 and 30 miles (30 to 50 km), occupied Arad and reached the approaches to Timişoara

The third stage of the 'Bucharest-Arad Offensive Operation' took the form of battles on the borders of Hungary. The Soviet supreme command still believed that Heeresgruppe 'Südukraine' had been defeated and ordered the Ukrainian 2^nd Front to deliver the main blow in the direction of Cluj, Debrecen and Miskolc with the objects of reaching the pre-war Romanian/Hungarian border, then of approaching the Tisza river in the Chop and Szolnok sector, and of aiding General Ivan Ye. Petrov’s 4^th Ukrainian Front, whose offensive was developing only slowly in the 'East Carpathian Strategic Offensive Operation', to cross the Carpathian mountains and take the Uzhgorod region.

This plan was not fully implemented, however. By 15 September, the German-led forces had managed to restore a continuous front from Ukraine to Yugoslavia. Although the Soviet forces went on the offensive and pushed back the German and Hungarian forces, the Germans transferred four divisions, two of them Panzer formations, to the area of Cluj and Turda. The 2^nd Ukrainian Front was already opposed by 27 German and Hungarian divisions and brigades, including six Panzer and Panzergrenadier divisions. Both sides continuously attacked and counterattacked, and the battle ended with a slight Soviet and Romanian advance: the Soviet-led forces threw back the German and Hungarian counterattacks and on 22 September reached the Romanian/Hungarian border to the north-east of Makoand. On the next day, the XVIII Tank Corps and 243^rd Division entered Hungary. On the front’s left wing, the 53^rd Army and the Romanian 1^st Army operated more successfully: on 21 September they liberated the large city of Arad and on 24 September also reached the old Romanian/Hungarian border.

In these circumstances, Malinovsky raised the question of changing the main offensive’s weighting from the centre to the left wing of his 2^nd Ukrainian Front, delivering a blow from here to the north and making a temporary transition to the defensive in order to prepare the new 'Debrecen Offensive Operation. The Soviet supreme command approved Malinovsky’s proposal on 25 September, but the 2^nd Ukrainian Front had already switched to the defensive on the preceding day and begun to regroup its forces.

As a result of the 'Bucharest-Arad Offensive Operation', almost all of central and western Romania had been taken from the German and Hungarian forces: the last small northern regions were seized in October 1944 during the 'Debrecen Offensive Operation'. The areas needed for the offensive into Hungary and Yugoslavia were now in Soviet hands. Large industrial areas and much of the railway network, as well as vital Romanian oilfields, had passed into Soviet hands with only minimal destruction. The 2^nd Ukrainian Front ranged from some 155 to 310 miles (250 to 500 km). In their efforts to restore the front, the Germans and Hungarians had been compelled to transfer to Romania 20 divisions (including four Panzer and one Panzergrenadier formations) and two tank brigades. The Soviet and Romanian forces had gained invaluable experience of successful collaborative warfare and, in general, the Romanians had showed good combat capability in the course of this complex operation: this last was in sharp contrast with its earlier unsuccessful military undertakings against Soviet forces.

The Soviet losses in this operation were relatively small: in a month of fighting, they amounted to 8,447 men killed or missing, and 46,839 men wounded or taken ill. The Romanian losses in the 'Bucharest-Arad Offensive Operation' are not known with any degree of certitude, but given the fact that between 23 August and 30 October their losses totalled more than 58,300 men, it can be assumed that in September 1944 the Romanians lost between 30,000 and 40,000 men killed and wounded.

The losses of the German and Hungarian forces are not known, but Soviet estimates put them at more than 100,000 men killed and more than 18,000 men taken prisoner. The degree of the German defeat is indicated by the fact that in Romania during September two German generals were killed in action, eight were taken prisoner and one committed suicide.