1915: The Austro-Hungarian–German advance into Russia

January–April 1915

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The 1914 campaign had ended in a stalemate in both the east and west. The German plan of a swift overthrow of France, to be followed by an unhurried reckoning with Russia, had miscarried. After less than a year of war, Germany’s Austro-Hungarian allies were already perilously near to breaking under the strain. From now onward, German formations had to be interwoven into the Austro-Hungarian battle line to stiffen its uncertain fabric.

On the other side, the weaknesses already evident in the Russian army were increased by the deficiencies in munitions, especially rifles and shells, which now began to be seriously felt. Even the severity of winter gave little check to the fighting. In the centre the front remained stable, but furious battles on either flank marked the opening months of 1915. On the Russian side, Grand Duke Nicholas had realized that he must secure his flanks solidly before any further attempt to advance in the salient. The question that divided Russian strategists was which flank to strike. The majority were for making an end of Austria-Hungary, while others urged, very reasonably, that the occupation of East Prussia would do more than anything else to solve Russia’s strategic problem. In the end, both were attempted and neither aim was accomplished.

Conflicting German plans on the Eastern Front

On the German side there now became evident a fundamental difference of opinion between Erich von Falkenhayn, chief of the imperial general staff, and Ludendorff, the guiding brain of the campaign on the Eastern Front. The latter aimed at nothing less than a decisive maneuver on the largest scale against the Russian armies, and he now urged that all available resources should be put into a great effort from both flanks, which was intended to finish the eastern campaign once and for all. Falkenhayn judged the distance too great and the communications too sparse for an operation on such a scale. He would allow only a limited offensive which sought tactical rather than strategic success. He hoped that a series of such victories would wear out the Russian army.

On the southern flank, battle raged all along the Carpathians from January to mid-April. The Russians sought to secure the crest of the mountains and to descend onto the plains below. The Austro-Hungarian force, stiffened by Gen. Alexander von Linsingen’s German Southern Army, strove to drive them back and to relieve Przemyśl. The result was indecisive; the Russians captured Przemyśl, which fell on March 22 and gained some ground in the Carpathians, but only at the price of terrible losses.

In the north, the grand duke had intended to strike his main blow with the newly constituted Russian Twelfth Army in much the same direction as Samsonov’s ill-fated offensive, but Hindenburg and Ludendorff forestalled him. Falkenhayn had, with some reluctance, consented to reinforce the Eastern Front with four newly constituted corps. The German Tenth Army was formed in East Prussia. With this force, along with the Eighth Army, Hindenburg took the offensive against the Russian Tenth Army, which was stretched out over a wide front just inside the eastern frontier of East Prussia. In the Second Battle of Masurian Lakes (February 8–22), the Russians were completely surprised and soundly defeated, with the loss of 110,000 prisoners, four divisions being surrounded in the forests of Augustów. The attack of the Russian Twelfth Army in the latter part of February and the beginning of March was easily repulsed.

The German summer offensive: May–September 1915

During the latter half of March and in April, except in the Carpathians, there was a breathing space in the operations on the Eastern Front. Falkenhayn now decided on an offensive in the east on a large scale. His aim was to hammer the Russians into powerlessness so that he could then concentrate the main German forces in the west without fear for the collapse of Austria-Hungary. The French and British offensives of March had enabled him to judge the extent to which he could safely weaken his western front to provide the necessary forces for this endeavour. He determined on a breakthrough on the Dunajec River between the Carpathians and the Vistula, and he entrusted the operation to Mackensen with the newly formed Eleventh Army, which contained eight divisions from the Western Front. The concentration was carried out with great secrecy, and the attack, which fell on Gen. Radko Dimitriev’s Russian Third Army, was preceded by artillery fire on a scale hitherto unknown on the Eastern Front. Operations commenced on May 2 and were an immediate success. The Russians were driven back with heavy losses to the line of the San.

Meanwhile, the Franco-British attempts at relief offensives had shown Falkenhayn that the defense in the west could stand the strain, and he withdrew more divisions for a continuance of Mackensen’s offensive. Italy declared war on May 24, and Falkenhayn had some difficulty in dissuading the Austro-Hungarian command from weakening their Galician forces. Mackensen crossed the San, retaking Przemyśl on June 3 and Lemberg on June 22. Large numbers of prisoners were captured, and the whole Russian command was much shaken. The Turks, hard pressed in Gallipoli, were relieved from the menace of a Russian corps which had been training at Odessa for an attack on Constantinople. This unit, and all other available Russian reinforcements, were thrown pell-mell into Galicia. The Russians were by no means broken, and they still counterattacked vigorously.

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Falkenhayn decided to continue the offensive but now with an eye on the clock. The Allies in the west were obviously preparing fresh attacks, which would probably develop not later than September. There was once again a sharp conflict of opinion between him and Ludendorff as to the plan on which the offensive should be continued. Ludendorff urged a decisive attack on Kovno and toward Wilno (Vilnius) and Minsk, with the object of cutting the Russians’ main line of communications. A German force had, at the end of April, crossed the north part of the East Prussian frontier and established itself at Libau (Liepāja). It was thus well placed to facilitate Ludendorff’s proposed operations by turning the line of the Niemen (Neman) River, provided it were made sufficiently strong to overcome the Russian forces which had been sent north to oppose it and protect Riga. Falkenhayn would have nothing of this bold plan, which he feared would commit him too deeply into the interior of Russia. He ordered instead a continuation of Mackensen’s offensive northward between the Bug and Vistula toward Brest-Litovsk. Hindenburg was to support Mackensen with an attack through Przasnysz on the line of the Narew River.

The Russian retreat

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Germany’s July offensives were successful, but only after heavy fighting. Thus, the grand duke was able to withdraw Russian forces from Warsaw and the salient while his line of retreat was still open. The failure to destroy the Russian forces in Poland intensified the conflict between Falkenhayn and the Eastern Front command (Hindenburg and Ludendorff). The former accused Hindenburg of not prosecuting the attack on the Narew with the full strength at his disposal. Hindenburg had, in fact, kept certain formations in hand for Ludendorff’s Kovno-Wilno scheme, thus allowing the Russians to escape. Hindenburg retorted that his advance on Wilno, if permitted, would have cut off the whole Russian army and ended the war in the east.

It was now the middle of August. Falkenhayn was compelled to return troops to the west to meet the impending French offensive in Champagne. He therefore ceased any further attempts on a large scale in the east. He had already accomplished his goal; in prisoners alone the Russian losses amounted to 750,000 troops, and the Russian armies would obviously be incapable of any offensive for many months. He left Hindenburg to continue the campaign and withdrew his objections to the Wilno advance, should Ludendorff still judge it feasible. Mackensen was taken to hammer out a fresh victory in Serbia.

During the latter half of August and all of September, the Russian retreat continued, pressed by constant German and Austro-Hungarian attacks. Ludendorff attempted his Wilno maneuver; although Kovno, Grodno (Hrodna), and Wilno fell, the Russians, by hard fighting, kept open their lines of retirement. At the end of September, the retreat was finally stayed on the general line that stretched from Riga in the north, southeast to Dvinsk (now Daugavpils, Latvia), and south to Pinsk and Dubno and ended at Czernowitz (now Chernivtsi, Ukraine) near the Romanian border. Early in September Tsar Nicholas II had taken over the chief command from Grand Duke Nicholas. His chief of staff and the virtual commander-in-chief was Mikhail Vasilyevich Alekseyev, a career soldier who had planned the Russian offensive into Galicia.

The strength of the Russian armies at the front had by this time sunk to 650,000. More than eight million men had already been mobilized, but the losses had been enormous. Russian morale was low, and there was a feeling that the Western Allies, by sitting inactive during Russia’s trial, had ill repaid the sacrifices which Russia had made for them in 1914.

The Brusilov offensive

The German assault on Verdun began on February 21, and on March 18, at the request of French commander in chief Joseph Joffre, the Russians started a relief offensive on their Western Front. The point of attack chosen was on either side of Lake Naroch (Narach), east of Wilno. After a preliminary success, the Russians persisted in attacks although a thaw had rendered the ground practically impassable. By the end of March, they had lost 150,000 men and had little to show for their losses. The Russians then commenced to prepare an offensive south of Lake Naroch, to take place in July, in combination with the Franco-British offensive in the west. Gen. Aleksey Brusilov, who had succeeded Ivanov in command of the Southwestern Front, had been ordered to prepare such offensives as he could stage with his own resources, to serve as distractions to the enemy from the main Russian effort.

In the middle of May, Austria-Hungary, contrary to the wishes of the German Supreme Command, made an attack on Italy which initially met with considerable success. Italy appealed to Russia to pressure Austria-Hungary and prevent the Austro-Hungarian formations deployed on the Eastern Front from crossing over to Italy. Brusilov’s offensive, loosed on June 4 in response to this request, shattered the Austro-Hungarian lines. The Austro-Hungarian front, from which the best troops had been withdrawn for the Italian attack, crumbled into collapse. The Russians, however, proved unable to take full advantage of their opportunity. Their reserves were all in the north and could not be moved down before the Germans could produce divisions to fill the gaps. Through the summer of 1916, Brusilov’s men continued their advance, but by the end of August they had lost their momentum. Bukovina and a large portion of eastern Galicia had been occupied and nearly 400,000 prisoners taken, but the Russian losses had been enormous. By the end of autumn, they amounted to something over one million on Brusilov’s front alone. Holding offensives made on the Russian Western Front at Baranovicze (Baranavichy) had also cost the Russians heavy losses with no gain. Outside Russia, Brusilov’s success had two important results—the entry of Romania into the war on August 27 and Falkenhayn’s replacement at Supreme Command by Hindenburg and Ludendorff.

The Romanian campaign: August–December 1916

Romania had been awaiting a favourable opportunity to throw in its lot with the Allies, and in August 1916 its time seemed to have come. The Russian conquest of Bukovina safeguarded the right flank of Romania’s intended advance into Transylvania. The German reserves seemed fully occupied in stemming Brusilov’s attacks in the east and the Franco-British offensive on the Somme in the west. The Bulgarians were, it was hoped, preoccupied with French Gen. Maurice Sarrail’s army in Salonika, an attack by which was promised. Encouraged by the French and the British, Romania took the plunge.

The prompt and united effort of the Central Powers against Romania was in contrast to the stark lack of unity between the Allies, particularly between Russia and Romania. Consequently, Romania’s adherence to the Allied cause was to prove an embarrassment rather than an addition of strength. The Romanian strategic problem was not an easy one. Its obvious defensive weaknesses included the long narrow salient of western Walachia projecting between Hungary and Bulgaria, the location of its capital within 30 miles (less than 50 km) of hostile territory, the exposed position of the Dobruja with no good natural barriers, the great length of its frontier line in proportion to the depth of the country, and the lack of lateral railways.

Only on the supposition that the Central Powers were too fully occupied to stage an offensive of any great weight could Romania have anticipated, as its leaders undoubtedly did, an easy victory. The invasion of Transylvania as the main operation was clearly indicated. It would give Romania possession of territory that it claimed by right of common nationality, and it would open the Carpathian passes to the Russians. Moreover, the occupation of a line about the Mureş valley, across the chord of the great bend of the Carpathians, would shorten the front by over 100 miles (160 km). A further advance westward would, however, have far to go before threatening any area vital to the Central Powers.

The initial Romanian offensive

The Romanians advanced in three columns, each about four divisions strong. The Fourth Northern Army seized the passes south of Bukovina and was to act in cooperation with the Russian left. The Second Army in the centre moved on Braşov, and the First Army moved through the Rothenthurm and Vulcan passes over the Transylvanian Alps to advance on Sibiu and Petrosani. A detachment of a division at Orșova on the Danube defended the left flank and rear. Three divisions were left in the Dobruja, to face the Bulgarians; by a provision of the convention under which Romania entered the war, they were to be supported by a Russian force of two infantry divisions and one cavalry division. Other Romanian detachments amounting to about three divisions held the line of the Danube. The whole southern front was under the Third Army command.

The plan of the Central Powers provided for a concentration in Transylvania behind the defensive line of the Mureş River. This group was to launch a counteroffensive against the Romanian First and Second armies as soon as troop concentration was complete. Meanwhile, a Bulgarian army, assisted by a German detachment and Austrian bridging train—the whole under the command of Mackensen—was to carry out an immediate invasion of Romania’s “back door,” the Dobruja.

Mackensen’s counterstrike

The Romanian advance was slow, and the Austro-Hungarian–German concentration on the Mureş was completed without interference. Meanwhile, Mackensen had achieved an outcome of far-reaching importance. He stormed the strongly fortified bridgehead of Turtucaia (Tutrakan) on September 5, capturing almost the whole of two Romanian divisions, while a third Romanian division was defeated and driven northward. Silistra fell on September 9. The Russian forces which now came up succeeded in saving, for the time being, the Constanța-Cernavodă railway. A Romanian counterattack in the Dobruja and an attempt to cross the Danube at Oryahovo in Mackensen’s rear were badly combined and executed and failed completely.

Operations in the Dobruja came to a temporary standstill early in October. Mackensen’s intervention had had the desired effect of halting the main Romanian offensive and drawing the available reserves southward. A counteroffensive in Transylvania was now launched. The Romanian First Army was beaten at the Battle of Sibiu (September 26–28), and their Second Army was decimated at Brașov on October 8. The Romanians were driven out of Transylvania and thrown on the defensive all along their frontier. Relations between the Russians and Romanians, already strained, were not improved by Mackensen’s defeat on October 19 of the Russo-Romanian Dobruja Army and occupation of the port of Constanța and the railway to Cernavodă.

The fall of Bucharest

The Romanians checked the enemy’s attempts to cross the passes on the heels of their retreat from Transylvania and compelled them to pause and await fresh reinforcements. They also defeated the first attempt of Falkenhayn, who commanded the principal Austro-Hungarian–German army, to force the Vulcan and Surduc passes. A second attack with fresh troops, made at the same spot (November 10–17), broke their resistance, and the Romanians fell back to a line astride the Olt River. Falkenhayn had won his race against winter by only a few days, as snow would soon have made large-scale operations in the high passes almost impracticable.

As soon as Falkenhayn’s army was across the mountains and within striking distance of the Romanian capital, Mackensen made the next move in the carefully orchestrated plan. Leaving a small force to hold the narrowest part of the Dobruja north of the Constanța railway, he withdrew the bulk of his army to Sistova (Svishtov). There his engineers bridged the Danube, and on November 23 his main force crossed the river, thus appearing in the rear of the main Romanian defensive line on the Olt. Both Mackensen and Falkenhayn now advanced on Bucharest, which fell on December 6, after a hard-fought battle on the Argeş River. The steadfast performance of what remained of the outnumbered and outgunned Romanian army owed much to the leadership of Gen. Constantin Prezan, who had now become chief of the Romanian general staff. Tardy Russian attacks in the Carpathians and the Dobruja had no effect, and the Russians and Romanians withdrew to a defensive line along the Siret and Danube rivers to the Black Sea.

Sarrail’s promised offensive on the Salonika front had been made with little apparent determination and brought no relief. The Romanian campaign had given the Central Powers control of the oil and wheat of Walachia and added 300 miles (480 km) to the already overlong Russian front. On the Allied side, it had been a badly mismanaged affair almost from the outset. The plan of the Central Powers was boldly conceived and skillfully executed. The careful coordination of the moves by Mackensen and Falkenhayn anticipated the mobile warfare of World War II. The Romanians suffered approximately 350,000 casualties (including 150,000 missing or captured) against roughly 60,000 for Germany. Austro-Hungarian and Bulgarian casualties numbered in the hundreds of thousands.