As noted, they weakened their forces because of the Russian attack in Prussia (which failed before the reinforcements got there)
This has always struck me as a somewhat amusing historical oddity.
For those who don't know what
@Cincydawg and I are talking about, here is a somewhat oversimplified brief explanation:
In 1870 Bismark goaded Napoleon's nephew who was then in control of France into declaring war against Prussia. You have to realize that this was only about 50 years after his Uncle had terrorized and invaded nearly all of Europe including briefly holding Moscow and at one point having a navy (including allies) large enough to credibly threaten to invade Britain.
Most neutral observers thought that France would crush the upstart Prussians. Britain, had been Napoleonic France's arch-nemesis and Prussia was an ally of Britain in the Napolonic wars including providing most of the ground troops at Waterloo. Additionally Britain and France had been enemies/rivals for centuries and the French were Catholic whereas the Prussians were mostly Protestant like the British.
My point is that Britain's natural sympathies were with the Prussians. Nonetheless, British newspapers were printing probable French invasion routes into Prussia in the belief, as I noted above, that the French would win. Instead the Kaiser's troops enveloped and annihalated the French Army at Sedan. Prussia unified most of the German people, the German Empire was declared and the Prussian Kaiser was crowned at Versailles.
The brand new German Empire immediately was the most powerful country on the Continent and over the next 45 years the other European powers set up a series of alliances in an attempt to provide for their defense and also to maintain a balance of power.
Schliefen was a German General who came up with Germany's plan for what was probably an inevitable war with France and Russia. Schliefen himself died before WWI but his plan was still in place when Archduke Ferdinand was assisinated in Sarajevo which ultimately set off WWI.
Schliefen assumed that it would take the Russians many months to fully mobilize and organize so his plan was to defend East Prussia with basically a token force while the vast majority of the German Army swept through Belgium to crush France and knock them out of the war quickly enough that the troops could be freed up to take on the Russians.
Schliefen's plan also specifically called for the last man on the right to "brush the channel with his sleeve". This served two purposes:
- It would keep the entire French Army inside the giant German net intended to close around them, and
- It would make it difficult for the British to intervene by capturing the French Channel Ports at which British troops would otherwise disembark.
Schliefen is said to have died muttering "Only make the right wing strong!" He fundamentally understood that technology had reached a point that massively favored the defensive so he knew that Germany could defend their Eastern frontier and their border with France with very small forces but they would need overwhelming numerical superiority for their offensive on the right.
Incidentally, the French war plan was almost a mirror image of the German plan as they also intended an advance by their right wing. Consequently, when war broke out the French and Germans were each attacking on their right and defending on their left such that when viewed on an overall map it looks like they are trying to go counter-clockwise through an enormous revolving door centered on Luxembourg.
Anyway, the French attack in the South (the French right wing) was a massive failure with the Germans easily stopping them. Meanwhile, the German advance through Belgium and into Northern France was quite successful although it added two new nations to the growing list of Germany's enemies and ultimately did them in some years later.
While all of this was transpiring in the West, the Russians managed to launch an invasion of East Prussia. As it turned out this invasion was disorganized, poorly supplied, poorly led, and generally a disaster for the Russians. However, it served a valuable purpose, it spooked the Germans. Moltke (German overall commander) pulled troops out of the right wing to reinforce East Prussia. The troops pulled from the right wing were in the process of moving East when Ludendorf and Hindenburg obliterated the Russians in East Prussia. At that point Moltke ordered them back to the Western front and they were in the process of moving West when the French stopped the German advance on the Marne.
Thus, the troops did no good for the Germans at all. Had they simply been left in the right wing there is a good chance that the French counter-attack would have been overwhelmed, France would have fallen, and Germany would have won WWI.
