The Battle of Tannenberg – SIGINT

A German communications squad behind the Western front, setting up using a tandem bicycle power generator to power a light radio station, much later than the 1914 Battle of Tannenberg, in September of 1917.

The German High Command’s nightmare was to be involved in a war on two fronts, but that is precisely what happened in 1914: they faced the Russians on their borders in the east and the French and British in the west. The majority of Germany’s troops were committed to the Schlieffen Plan, an offensive formulated by General Schlieffen, which planned to attack France by passing through Belgium. The German strategy was to hold back the Imperial Russian Army using defensive tactics while seeking a swift decision over the French and British in the west. The High Command estimated that the Russians would need about six weeks to mobilise their immense army, but the Russians surprised everyone by going into action sooner than expected. They crossed the border and advanced well into East Prussia within days of war being declared and the way to Berlin was open. An early Russian victory could have knocked Germany out of the war within weeks and the implications of this opportunity were immense; if the Imperial Russian Army had advanced on Berlin then Germany would have had to admit defeat. There would not have been the dreadful slaughter and suffering of the next four years and it is even possible that the Second World War would not have happened.

The Imperial Russian Army had 416,000 men and almost 1,300 guns in the field, twice the size of the German Eighth Army facing them, which mustered 166,000 men and 846 artillery pieces, commanded by General von Prittwitz und Gaffron. The Russians were divided into two armies: the First Army with 210,000 men was commanded by General von Rennenkampf; and the Second Army with 206,000 men by cavalry General Samsonov. It was said that these two officers disliked each other but, for whatever reason, the fact is that they did not work well together. Prittwitz had earlier fought the indecisive Battle of Gumbinnen against the advancing Russians, the outcome of which was to position the armies in a way that would decide the course of the future campaign. After the battle, Prittwitz exuded defeat and talked of retreat to Berlin in long telephone calls to his superior General von Moltke in his headquarters in Koblenz, over 1,000km away. The telephone network that the German government had installed a few years before was going to repay them handsomely. Prittwitz was immediately sacked by telephone. A few years earlier it would have taken a messenger on horseback a week to deliver the news by a written despatch. A further telegraph message to 66-year-old General von Hindenburg brought him out of retirement to lead the Eighth Army; he famously replied ‘Am Ready’ and immediately took command. He appointed von Ludendorff as his chief of staff and made plans to fight the battle in a place called Tannenberg. The battle was to prove the first military engagement where the emerging radio technology would play a decisive role. This was remarkable because the German intercept service hardly existed, but signals intelligence gave Hindenburg a decisive advantage just by listening to Russian radio traffic.

Two Russian armies crossed the German/Russian border and pressed on past the Masurian Lakes, which consisted of a series of stretches of water and marshes just north of Warsaw; the lakes separated the two armies, with First Army passing to the north of these watery obstacles and Second Army to the south. Hindenburg decided that he would attack Samsonov in the south if Rennenkampf’s First Army, some distance away in the north, was not in a position to attack his flank. The Germans had five of the new mobile radio stations for their army, but it was the heavy ones in their fortresses of Koenigsberg, Graudenz and Thorn that were going to count. There was little transmission traffic in the fortresses to keep the operators busy so they listened to Russian transmissions to pass the time. The Imperial Russian Army was equipped with the most up-to-date wireless sets which were attached to every large formation of their army. Unfortunately for them, their operators were not well trained; in fact, not trained at all. The possibility that their messages could be heard by the enemy probably had not occurred to them so they sent virtually all their messages to each other in clear text. A Russian message was intercepted by Fortress Thorn indicating that Rennenkampf would not pursue retreating German forces to his front. On the initiative of the commandant Colonel Nicolai, the message was immediately despatched by motorcycle to Hindenburg. This was probably the world’s first electronic interception of a military signals message in battle conditions and it was an important one. As a result, Hindenburg decided to let the whole weight of his Eighth Army fall on Samsonov’s Second Army. The value to the Germans of this intercepted message was incalculable.

As battle intensified the Russians sent all their radio communications in plain text, not appreciating the finer points of radio security. They were to pay a heavy price, as the Russian General Danilov wrote in his report after the battle on their communications failures: ‘The use of radio was entirely new and therefore unfamiliar to our staffs. The enemy, however, were also guilty of some errors, although this does not absolve us from the charge of unpardonable negligence.’ Danilov considered that faulty functioning and, in most cases, non-existent use of radio security was the major cause for the Imperial Russian Army’s catastrophic defeat. The Russians became aware of some of the ways wireless communications could be used later, but they did not appreciate the importance of the maintenance of a dependable radio network until the beginning of the Second World War.

The Battle of Tannenberg began on 23 August as the Russians attacked German positions and several radiograms were intercepted revealing the Russian objectives, including their unit strengths and line of march. Two of the most important interceptions on the night of 24 and 25 August 1914 still reside in the Bundesarchiv and read:

To the Corps Commander of XV Corps

Your Corps will deploy along the Komusing-Lykusen-Persing line till 0900, at which time attack is desired. I shall be in Jablonica, Kljujew with XIII Corps

Then to the 2nd Army Chief of Staff

The XIII Corps will go to the support of General Martos XV Corps and deploy along the flank and rear of the enemy at 0900

This information enabled German generals to avoid an encirclement of part of their army. On the next day of the battle, 24 August, Hindenburg was handed another intercepted message containing the complete operational order of First Army, giving their objectives and timetable. A further intercept indicated that the Russians could not reach those objectives until the 26th, so that told Hindenburg that the Russian First Army would not be able to attack the flank of his army for a couple of days. This gave him time to deal with the Russian Second Army passing to the south of the Masurian Lakes. He moved his headquarters southwards and, on his way, received another intercepted message on the 25th, still in plain text, with details of the organisation and destination of the Second Army. It also contained a somewhat garbled order from General Samsonov to a corps of the Second Army. The text omissions we represent as ‘…’ so the text reads:

After battling along the front of the XV Corps the enemy retreated on 24th in the direction of Osterode. According to information … the land defence brigade …The 1st Army pursues the enemy further, who retreats to Konigsburg-Rastenburg. On 25th August the 2nd Army proceeds to Allenstein-Osterode line; the main strength of the army corps occupies; XIII Corps the Gimmendorf-Kirken line; the XV Corps Nadrau-Paulsgut; the XIII Corps Michalken-Gr. Gardiene, boundaries between the army corps on advance; between XII and XV the Maschaken-Schwedrich line; between XV and XXIII, the Neidenburg-Wittigwalde line. The 1st Corps to remain in District 5, to protect the army’s left flank … The VI Corps to advance to the region of Bischofsburg-Rothfliess to protect the right flank. To protect station Rastenburg the 4th Cav. Div, subordinates to VI Army Corps will remain in Sensburg to observe region between Rastenburg-Bartenstein line and Seeburg-Heilsburg line. The 6th and 15th Cav. Div … staff quarters in Ostrolenka.

Hindenburg now knew the order of battle of both Imperial Russian Army’s and the other intercepts gave him their objectives.

Another aspect of the battle determined by the interception of plain text transmissions was the manoeuvring and engagement of the Russian XIII Corps of the Second Army at Allstein. Hindenburg was completely in the dark as to this unit’s position and its intentions, but he was concerned that it represented a threat to the flank of his own Eighth Army. During the morning of the 28th, further intercepted radiograms describing the Russian XIII Corps’ movements and intentions were received. In an innovative move, orders were despatched by airplane to Hindenburg’s reserve forces to counter Russian moves. Further intercepts allowed him to feel safe in concentrating German forces on the destruction of the Russian’s Second Army. Hindenburg’s victory was one of the most complete in military history, with 78,000 Russian soldiers killed or wounded against 5,000 Germans killed and 7,000 wounded. The Germans took 500 guns and 92,000 prisoners. This savage blow kept the Imperial Russian Army off balance until the spring of 1915 and probably accelerated the Russian Revolution. Meanwhile, Rennenkampf’s army had gone on the defensive until Hindenburg attacked him, so consequently the Russians drew back beyond their own borders with very heavy losses.

One of Hindenburg’s last strokes in the campaign was a deception using radio transmissions. During the Masurian Lakes campaign later in September, he needed to mislead the Russians into tying down their large reserve force around the city and fortress of Koenigsberg. Hindenburg had no extra troops available to engage this reserve force so he decided on a tactic of misinformation. On 7 September the radio station at Koenigsberg sent a purposely disjointed message:

To the Corps Chief, Priority Telegram

Guard Corps

Tomorrow the Guard Corps will join the … Immediately west of Labiau, parts of the V army unloaded

Army Staff Headquarters.

The Russians intercepted this deliberately plain text message and were completely taken in by it. The Russian reserves did not move to support their comrades who were under attack, but waited patiently for an attack from a German formation that did not exist. This is one of the first recorded ‘double cross’ messages that became an art form later in the war and particularly in the Second World War. German operators began to recognise the style of Russian transmitters, but were put under orders not to jam them on the principle that a poorly secured transmitter was of such value as an intelligence source that they should be given a clear field. As Napoleon said, ‘never interfere with the enemy when he is making a mistake’.

The Battle of Tannenberg and the following campaign were shaped by a number of things. The Russians crossed the border into East Prussia just a few days after war was declared. They were able to move quickly because they had not taken the time to prepare the logistic supplies and neglected the needs of their armies in the field. Also the German Army was of superior quality to the Russians, having better equipment, training and leadership. Rapid movements using Prussia’s rail system enabled the German staff to entrain and move complete corps formations around the battlefield and concentrate them against threats or opportunities posed by the enemy. Russian signals transmissions consisting of over a hundred messages in plain text had enabled Hindenburg to know the enemy’s position, strength and intentions days in advance of their being committed to action. None of these advantages would have been worthwhile if the German commander had not been a superior general who was able to inflict grievous damage on the Russians at little cost to himself. His victory virtually cancelled out the threat of the Imperial Russian Army on Germany’s eastern border, enabling the German High Command to concentrate on the battle in France. However, on reflecting on the battle, Hindenburg said almost nothing about the intercepted messages from which he had benefited.

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