Wow, good map of plan XVII! Where did you find it?
Here I have my question marks. After reading this article about
British entry into World War I, I draw different conclusions. Britain certainly wants to avoid a French defeat. But to join France, after France itself declares war and invades Germany... That is highly unlikely. Britain will impose conditions on Germany under which it remains neutral (no HSF in the channel, for example). Germany is forced to adhere to that.
Plan XVII was disastrous for France, as evidenced by the
Battle of the Frontiers. Lorraine will also be a slaughterhouse for France in this TL. After that, Germany is certainly capable of a counterattack, just like in OTL.
Hm ... the 8th army is not mentioned. Perhaps a very old source?
This article on German deployment plans mentions other divisions between east and west. 5 German armies on the western front is more likely. Then your assumption about the course of the battle will not come true.
The French official history of WW1 is online and has a ton of great maps! See
here!
The Wikipedia article offers a weak summary and takes Zara Steiner in
Britain and the Origins of the First World War out of context. While the invasion of Belgium proved key to providing the
justification for war and fully galvanizing support, the
decision had already been made up by August 2nd, with a majority of the cabinet accepting the rationale for war:
Political considerations contributed to the near unanimity of the Cabinet. It was not that the neutralists deserted their principles to stay in power.59 Grey’s question forced his colleagues to consider those interests which had led them, despite occasional outbursts of indignation, to support an Entente policy with its accompanying strategic dispositions right up to the eve of the war. Only a small minority had clearly rejected the balance-of-power theories which underlay Grey’s thinking. Few wished to go as far as Grey was now demanding, but there was a growing sense that intervention was inevitable. Britain had not been attacked but with France involved, all the past reasons for strengthening the Entente came into play. Politicians seldom resign voluntarily, especially for a lost cause. Ministers already knew that if Grey’s Entente policy was repudiated, he and Asquith would leave the Cabinet and others would follow. The arrival of the Conservative leaders’ letter pledging ‘to support us in going in with France’ strengthened Grey’s hand at this crucial meeting.60 There was a clear alternative to a Liberal government.
While a German non-invasion of Belgium would certainly have prompted at least some additional cabinet resignations, the balance of power both within the Liberal cabinet and Parliament at large had decisively shifted. Had the cabinet refused to countenance war, the Conservatives were waiting in the wings to take advantage of the resignations of the interventionists to rope disaffected pro-war Liberals and Labor MPs, 1/4 -1/2 of both parties, into a war coalition. It was either going to be a Liberal war or a Conservative. Wilson's article "The British Cabinet's Decision for War, 2 August 1914
" states this point forcefully as well, which Clarke in
The Sleepwalkers agrees with.
Faced with desertion by Grey and Asquith, their most prestigious colleagues, and with the readiness of the Opposition to pursue a war policy, the neutralists had reneged on their pacifism. Considerations of unity and of the future prospects of the Liberals as the party of Govern meant constrained all but four ministers (even though a contradiction of one of the basic tenets of Liberalism was involved) to accept the conditions Grey made.
Whether France declares war on Germany in defense of Russia isn't relevant to the calculation here, which is a matter of imperial sentiments and parliamentary politics. It does make it harder to endorse a fullscale armed commitment to the continent, however, which is why I imagine Asquith would square the circle by initially pursuing a blockade + colonial warfare, with armed forces on the continent only if Germany invades Belgium.
As to Plan XVII, I'd suggest reading Doughty's article "French Strategy in 1914". Plan XVII was a plan of concentration, nothing more. Joffre made the call on where to attack based on where he believed the Germans were weak. IOTL he assumed they had fewer divisions than they actually did, and therefore attempted to launch assaults into the Ardennes and Lorraine where he believed the front was screened only by weak reserve corps (Crosshatched areas):
This of course proved incorrect. Joffre's offensive in Lorraine with 6 Corps ran smack into 8 German Corps who counterattacked and defeated them in detail. 3rd and 4th Army in the Ardennes fought 10 German corps with 8 French and were also defeated. And we know how the BEF and 5th Army were handled by 3 German armies. Going on the offensive wasn't a bad idea, conceptually, to throw off the German plan - going on the offensive with dispersed strength on multiple axes with bad intelligence against a numerically stronger enemy was. In An ATL, a strong concentrated offensive against a weaker opponent would be exactly the right call.
This is not to say the French defeat was solely the result of strategic errors. They had obvious weaknesses at the operational and tactical level which took several weeks to overcome. However, France on the offensive will benefit greatly from the ability to concentrate in strength against a numerically inferior enemy, as the Germans did successfully on several occasions. Fighting a battle of maneuver in Lorraine against a numerically superior French Army is not going to be a fun experience for 5th, 6th, and 7th Armies. Writing off the French Army which inflicted 200,000 casualties on the Germans in August and defeated them just 2 weeks after losing at the Frontiers would be relying too much on cliches and stereotypes over history.
To your final point, I believe Wikipedia is confusing different deployment directives. To sum up they are:
Aufmarsch I - Deployment directives if the war begins in the West. It had 2 variants, Aufmarsch I West (The "Schlieffen Plan") or Aufmarsch I Ost, which deploys 3 armies in the East and 5 in the West.
Aufmarsch II - Deployment directives if war begins in the East. It had variants Aufmarsch II West (Again, the "Schlieffen Plan") and Aufmarsch II Ost (The "Grosser Ostaufmarsch") which deploys 4 armies East and 3 armies West.
Aufmarsch II Ost was built on in the late 1900s and Early 1910s in response to the Balkan crises and growing Russian military power. It was a plan to strike at Russia offensively in the event of a general Balkan war, with a strong defensive force in the West if France joined Russia's side at some point. As I noted above, this involves deploying 42 divisions in 4 armies East and 34 divisions (Plus 2 Corps in reserve and 6 Ersatz divisions) to the West, keeping at their mobilization stations to respond to a French invasion. In 1912-1913 this was the only war plan under serious consideration in response to the Bosnian Crisis.
Aufmarsch II Ost had some obvious flaws. Deploying 2 armies of 10+ Corps to East Prussia over just a couple double track railway lines would take substantial time, as long or longer as it would take the Russian Army to fully mobilize. Deploying 2 additional armies to East Prussia would take even longer, but so would deploying them in Silesia/West Prussia and having them march to the Vistula/across the Vistula to the Narew, respectively.
But it's the best plan to focus on knocking out Russia ASAP, and was the only one the German Army had on the books from 1900-1913. From 1913 onward Moltke focused entirely on France and Aufmarsch I/II West. But ITTL the Kaiser insists on an Eastern deployment, and so the Grosser Ostaufmarsch is brought back into play.