Germany had a war plan as late as 1912 for a mass vs. Russia with roughly half the army.
In any case Wilhelm II nearly caused Moltke to have a break down when he announced that they could ignore France and go after Russia following a telegram from the Ambassador in London that later turned out to be false.
Is it possible to get Germany to mass vs. Russia as late as 1914? Yes but it requires some changes as lone war plan from 1913/14 on was everything vs. France. One choice is for the crises to play out differently. Another is for Conrad to dig his heels in over his mobilization debacle because the way that was playing out was getting the Germans worried. Maybe have that go even worse, such that Germany feels that they have no choice but to improvise something; the Germans hadn't started mobilization yet so there was an opening.
If the Germans mass east its going to take two extra weeks for all the troops to arrive in theater. Depending on what exactly they do you end up 4 armies in East Prussia or 3 in Prussia with the 4th in Silesia; something like that.
My two bits is UK sits on the side line for at least week with no Germany in Belgium to provide the provocation. French plow into A-L and you get a blood path there. The question mark is what does Russia do.
I really wonder if they would be capable of moving the armies once in motion; 4th army which was assigned to Germany or Austria-Hungary depending on the setup. Would there be time to have the 4th redirect towards Germany once it became clear that Germany was massing East? France and Russia had agreement to do combined offensives by X days after mobilization, 15 days I believe (this is the 1st and 2nd Russian armies into East Prussia).
Maybe Russia improvises successfully, maybe they try and botch the improvisation and so the 4th army ends up on nether front for first week or two of the fighting or maybe Russia just ignore things blows a head ignoring the situation. I suspect Russia drags their feet in responding to the German stance (4th army gets set to Galacia and then moved later) and they go forward with their scheduled offensive so 1st and 2nd armies get chopped to bits. Thats me, others may differ in how much credit they give the Russia high command, I don't give it much.
Even if the Russians don't botch the opening moves of the war like I am suggesting and even if they go defensive with 1st and 2nd armies, there is going to be a big shift in combat power in the east. There is all sorts of butterflies to consider for A-H. Russia is going to have to sooner or later switch troops from Galacia to Poland to face the bigger German threat. Which takes pressure off A-H. Conrad botched the opening 6 months of the war as complete as possible and really badly damage the army; anything that improves this can only help the efficiency of the Hapsburg army over the course of the war. By end of 1914 I figure Warsaw has fallen and the Germans have or will soon have most of Congress Poland. By end of 1915 the Germans are deep into the Baltics.
Long term question is does UK stay out? When does France give up on trying to head but their way into A-L?
Michael