As for Germany winning a long term war. That is not happening.
Since there's no way Germany can defeat the Entente (in any form) in one campaigning season, you must therefore be arguing that Germany should not go to war at all, yes?
As for the idea of going East First. This is insane. Russia is huge and has tons of territory to give up and keep fighting. Plus Russia has a huge population it can mobilize.
On the latter assertions: Sure and sure.
And yet - Russia still was defeated in the Great War!
But the Germans in 1914-18 did not attempt to replicate the strategy of Batu Khan, Chodkiewicz, Charles XII, Napoleon . . . or, well, Hitler. There was no attempt to overrun the Russian heartland. Their operations were confined to the regions of the "Captive Nations" and actually made some efforts to cultivate these peoples as allies. All while grinding down a deeply inefficient and badly supplied Russian Army. The result was a weak autocracy increasingly unable to sustain popular support for a war in which Russian national survival did not appear to be at stake, or even support for its own continued survival as a regime. The result was revolution and, before long, Brest-Litovsk.
The objective of a Russia-first strategy for Germany in the 1910's is not to conquer Russia, but to defeat it through a war of attrition its government cannot sustain. Its larger strategic justification over the alternative of France-first is to avoid British belligerency and thus a larger coalition in which the correlation of forces no longer favors the Central Powers.
Which brings us to...
And anyone thinking GB will stay out is utterly falling for the propaganda. GB is getting intro this war. First off it has treaties with Russia and France, Second it does not want ANYONE dominating Europe or dictating peace terms unless GB gets a say in the terms and in order to do that they have to be in the war. So GB is entering the war.
How often this is asserted without any substantive examination of British policy making under Asquith - and regrettably, I cannot see how your claim is any different.
In the first place, some correction is in order:
Great Britain had no treaties of mutual defense whatsoever with France or Russia in 1914. What it had were conventions with each power (France in 1904; Russia in 1907) to settle outstanding colonial disputes in Africa and Asia. There were secret military discussions, beginning in 1911, between the British and French general staffs over possible deployment of a British expeditionary force in a potential war with Germany; but these were nothing that legally required British belligerency under any circumstances whatsoever. Even Grey admitted this point to the Cabinet on August 2 and in his speech to the Commons on August 3. Neither Asquith or even Balfour could have sold such an alliance treaty to Parliament. Even the Anglo-Japanese Alliance treaty (the only formal mutual defense treaty Britain had in 1914) did not require British belligerency if Japan went to war!
It's true that the ultimate, real motivation for Grey and Asquith was to prevent the obliteration of France as a great power able to help balance Germany - especially if this meant German control of North Sea and Channel ports of Belgium and France. But this prospect is only in view in a
German invasion of France and Belgium. And it needed that to sell a declaration of war to Parliament (controlled by Asquith's party, but a party also dominated by non-interventionist sentiment) - and the British public - which is why the two premises Grey finally needed to persuade the Cabinet to create an ultimatum to Berlin on August 2 were demands that 1) no German naval units enter the Channel, and 2) Belgian neutrality be respected.
A situation in which France declares war on Germany rather than the other way around is a fundamentally different one for any government in Whitehall in 1914 - even a Tory government. The Boches aren't coming to Nancy, let alone Paris.