The Eastern Front Part 3 -The invasion of East Prussia and the battle at Gumbinnen

The Masurian Lakes forced
the Russian advance into a north
and south enveloping strategy

It may be a harsh judgement on a different era, but by today's standards, WW1 Generals come across as insufferably arrogant individuals. Of course there were exceptions, but here is another example of how jealousies between commanders on the same side, compounded by abysmal communications, shaped a terrible fate for one of the combatants - in this case Russia at Tannenberg.
Jilinsky, previously Russian Chief of Staff - very much a HQ man -  commanded the 1^st and 2^nd Russian armies facing Prussia at the NW end of Russia’s front. He had little time for the two Generals at the sharp end, and was much more concerned about his stock within the political mood music from the centre. In turn, Generals Rennenkampf (1st) and Samsonov (2^nd), ranged against a small German 8th Army, had no time for each other (or for Jilinsky for that matter). They were both good generals, but fierce rivals from earlier battles in Manchuria, and neither was minded to put himself out for the sake of the other. Jilinsky's priority was to invade East Prussia with all possible speed. This was mandated by the Russo-French treaty of 1911, and by pressure from St Petersburg (urged on by the hysterical French Ambassador Paleologue), and remote from the realities of terrain, shortage of supplies and almost absent communications.  

Maximilian von Prittwitz

The German commander facing them was Maximilian von Prittwitz, another unpleasant and much disliked character. Prittwitz, nicknamed ‘the fat soldier’ was held in low regard by his younger and more vigorous senior officers. He was outnumbered by 3 to 1 in infantry, and thought to be in a very weak position. However, in addition to having excellent senior officers, including Francois, Mackensen and Below, he had the advantage of the Masurian lakes – a 50 mile stretch of impassable lakes and waterways – that would inevitably split the advancing forces. Using their efficient railway networks, superior equipment and communications, the Germans were able to switch rapidly their forces from one end of the lakes to the other.

Paul von Rennenkampf

The nature of the terrain - marshes and lakes, with few good routes passable for men and equipment - dictated a two pronged advance into Prussia. The plan was for Rennenkampf's army to pass by the north route, whereas Samsonov would pass to the south of the larger lakes. If things went well, this would deliver a classic pincer movement to trap and destroy the numerically inferior German army. This required decisiveness, good communications and co-operation between each claw of the pincer. None of these applied.

Prittwitz was cautious, however. Not unreasonably, he was strongly influenced by Moltke's stern warning that at the very worst he should not allow the Russians to reach the Vistula river, well to the West. He kept one corps in the South, and held the other two corps centrally to cover either move of the pincer.
                                                                                                                 

Alexander Samsonov 

He was persuaded by Francois to send the other forces north to meet head on the advance of Rennenkampf. On what is today's Russian Lithuanina border, they clashed with the Russians at Stalluponen (today Nesterov) and inflicted heavy losses on Rennenkampf. They engaged again, a few miles to the west at Gumbinnen on 20th August. 
Churchill writes “very few people have even heard of Gumbinnen, and scarcely anyone has appreciated the astonishing part it played (in the entire war)”. It was a tumultuous battle, with great German success on the flanks, but rout and panic in the centre as thousands of Germans fled in chaos to the west. News of this had a major effect on Prittwitz 75 miles away in his Marienberg (Malbork) quarters. Despite arguments from his Chief of Staff, Hoffmann, and his generals he resolved to withdraw all his forces to the line of the Vistula river, well to the west. In serious panic, Prittwitz then phoned Moltke, by then deeply involved in battles on the Western front, to beg for reinforcements. Moltke resolved to replace Prittwitz and his deputy Waldersee. He chose Ludendorff and Hindenberg.

(Hastings) “On the afternoon of 22nd August, Eighth Army’s headquarters at Marienburg on the western border of East Prussia received a terse message: Prittwitz was dismissed. The elderly General Paul von Hindenburg had been summoned out of retirement to relieve him; he would be accompanied into the field by a new army chief of staff, the bleak, moody Erich Ludendorff, fresh from his heroics at Liège.

Hindenburg was the man Berlin expected to transform the campaign, selected before Moltke gave a thought to identifying a figurehead commander-in-chief. Ludendorff was a commoner, forty-nine years old, who had risen by sheer ability through the ranks of an army dominated by aristocrats. A dour professional warrior to every extremity of his being, he considered war the natural business of mankind. He had served on the General Staff under Schlieffen, who remained his idol. For a decade he had enthusiastically endorsed the core principle of German planning – that East Prussia should be lightly held while France was disposed of.”  

Herman von Francois
defied Prittwitz and Moltke
to take the offensive

     During Gumbinnen, the Germans had intercepted Russian orders for the whole campaign, and knew of Samsonov's intentions in the south. So until Ludendorff and Hindenburg arrived, Hoffmann and other senior staff persuaded Prittwitz not to flee west to the Vistula, but to use the railway network to concentrate the German forces south of the lakes to face the oncoming Samsonov. This set up the historic battle of Tannenberg.

Most significantly, 25th August was the day Moltke, unnerved by Prittwitz’s panic, determined to send significant forces from the western front to the east. Moltke reasoned that the decisive battle in the west had already been fought and won, whereas two weeks later the forces he released would have provided vital back up at the Marne.