A Schlieffen Plan study

[Dazo]

Hi everybody [:)],

Had this idea for a while but never took the time to do it before today: a study (for lack of better word) on how to apply/execute the Schlieffen plan ingame and why it's a good idea to do it. I hope you'll find it interesting.

It's quite long and images are a bit small so I also converted it to a pdf with a download link (v3) :
PDF
(link updated 31 march 2025)
Edited to correct some typos and add more comments/details:
- USA small swing towards Entente thx to Bavre
- some numbers about NM gains

Also a youtube video link of this opening thanks to mdsmall to have a better dynamic view of it
(you'll see it doesn't always go as planned haha):
https://www.youtube.com/watch?v=ql3DtVv ... OHqDrBFC87

(READ from left to right and then top to bottom)
1-2-3
4-5-6
and so on...

ORIGINAL: 1775Cerberus

As an IMO addendum to executing the plan. Once the front does stabilize you can continue to bleed the French and British while using your internal lines to execute one of three strategies. Listed in my preference to execute.

1) Send a Army group of a HQ, Four Inf Corps, a Cav Corps, and the Artillery to Serbia/ Montenegro to push along the Adriatic coast in co-operation with an Austrian offensive in the north. Serbia cant survive this for a year w/o a significant allied intervention force on their behalf. If the allies do intervene then those are forces not available elsewhere. (Helping the Ottomans most likely.) This will also help the AH forces when the Italians join the war as the AH will have extra forces available, along with that Army you sent who can join that defense or go on ahead and take Salonika.

2) Send and build ALL available HQ and forces to Poland and begin to kill Russian Corps and take cities. Assuming that it is the fall of 15 by the time you are ready to launch the counter attack here you will still have advantage in "infantry warfare" Use it until Artillery becomes the hammer that drives the Russian nail.

3) Break off a HQ and a force similar to the one you sent to Serbia. Send this force to the Galician front. Use it as the hammer that allows the AH army to do the maneuver that will allow you to put Russian formations in a bad supply condition and soak up a lot of the initial attacks before the Germans move in and finish the fight. Doing this with a general direction of advance being the Caucus forces the Russians to defend on two separate fronts without the help of internal lines. Once you get things rolling watch the Russian morale sink fast.

[Espejo]

[&o] Thank you very much. This is a refreshing article as many players seem to ignore the original Schliefen Plan. I would be horrifed to see such a strong and determined advance of the German Forces into France

[Bavre]

[X(]
Hmm, I have indeed never tried to invade Belgium as the Central Powers. The short frontline with mostly well defensible terrain and no hexes bordering more than 2 enemies is just so tempting...
Are there severe diplomatic downsides, like pissing of the US?
The only time I ever saw Schlieffen in action was german youtuber Steinwallens lets play, but that was vs AI.
I must say I am kind of intrigued, would you like to try it out against a human opponent?

[1775Cerberus]

As an IMO addendum to executing the plan. Once the front does stabilize you can continue to bleed the French and British while using your internal lines to execute one of three stratagies. Listed in my preference to execute.

1) Send a Army group of a HQ, Four Inf Corps, a Cav Corps, and the Artillery to Serbia/ Montenegro to push along the Adriatic coast in co-operation with an Austrian offensive in the north. Serbia cant survive this for a year w/o a significant allied intervention force on their behalf. If the allies do intervene then those are forces not available elsewhere. (Helping the Ottomans most likely.) This will also help the AH forces when the Italians join the war as the AH will have extra forces available, along with that Army you sent who can join that defense or go on ahead and take Salonika.

2) Send and build ALL available HQ and forces to Poland and begin to kill Russian Corps and take cities. Assuming that it is the fall of 15 by the time you are ready to launch the counter attack here you will still have advantage in "infantry warfare" Use it until Artillery becomes the hammer that drives the Russian nail.

3) Break off a HQ and a force similar to the one you sent to Serbia. Send this force to the Galacian front. Use it as the hammer that allows the AH army to do the maneuver that will allow you to put Russian formations in a bad supply condition and soak up alot of the initial attacks before the Germans move in and finish the fight. Doing this with a general direction of advance being the Caucus forces the Russians to defend on two separate fronts without the help of internal lines. Once you get things rolling watch the Russian morale sink fast.

[Dazo]

ORIGINAL: Espejo
[&o] Thank you very much. This is a refreshing article as many players seem to ignore the original Schliefen Plan. I would be horrifed to see such a strong and determined advance of the German Forces into France

You're welcome Espejo, glad you find it interesting ^^ . That opening is a tone-setter for sure.
Being "horrifed to see such a strong and determined advance of the German Forces into France" is actually one of the benefits at least when you don't expect it or have never experienced it before because it's hard to decide how to react and Entente can even make some bad "panic" moves.

ORIGINAL: Bavre
[X(]
Hmm, I have indeed never tried to invade Belgium as the Central Powers. The short frontline with mostly well defensible terrain and no hexes bordering more than 2 enemies is just so tempting...
Are there severe diplomatic downsides, like pissing of the US?
The only time I ever saw Schlieffen in action was german youtuber Steinwallens lets play, but that was vs AI.
I must say I am kind of intrigued, would you like to try it out against a human opponent?

Hi Bavre, happy to see it opens new horizon for other players .
Good question about US, forgot that in the study. The diplomatic effects of DOW on Belgium are:
- UK joins Entente on turn 1
- US small leaning towards Entente (around 7%) which is negligible given their industrial base
As for the short front, try to picture a stabilized one running from south of Boulogne to Reims, it's only 4 hexes and the two hexes gap between Reims and Verdun has difficult terrain all around.
Total 7 hexes mostly with defensive bonuses so you just double the front and only need at least 4 more infantry corps to hold it once things calm down (better have more as reserves of course).
You may need more if you take Amiens or manage to stay closer to Paris since your advance will form a salient but you'll need most of your troops between turns 1 and 5 when you clean up Belgium while facing BEF and french units coming to the rescue.

ORIGINAL: 1775Cerberus
As an IMO addendum to executing the plan. Once the front does stabilize you can continue to bleed the French and British while using your internal lines to execute one of three strategies. Listed in my preference to execute.

Hi 1775Cerberus, thanks for adding those follow-ups to the plan and that's its beauty in the long run when well executed: you reap NM/MPPs benefits for quite a long time while having some room to deal with other fronts. Entente possible strategies to try to avoid that are another very interesting debate .

[1775Cerberus]

ORIGINAL: Dazo

ORIGINAL: 1775Cerberus
As an IMO addendum to executing the plan. Once the front does stabilize you can continue to bleed the French and British while using your internal lines to execute one of three strategies. Listed in my preference to execute.

Hi 1775Cerberus, thanks for adding those follow-ups to the plan and that's its beauty in the long run when well executed: you reap NM/MPPs benefits for quite a long time while having some room to deal with other fronts. Entente possible strategies to try to avoid that are another very interesting debate .

I do tend to take a very v. Falkenhayn approach to the game. Bleeding enemies till morale breaks is the key to the long game. Hence I have some very strong views as playing both sides. For the CP the room to breathe in the west is a vital key. The only way to do that is the Schlieffen plan, and fighting the urge to peek back over your shoulder at the Russians for the first three months or so.

This was very well presented sir. I tip my cap to you.

[Espejo]

First try in an MP game worked like it was supposed to. It simply surprised the Entente, scrambling to establish a front line and counter attack. Alas, to late to save the North.


Long story short an interessting way to make the game exciting

[Dazo]

ORIGINAL: Espejo

First try in an MP game worked like it was supposed to. It simply surprised the Entente, scrambling to establish a front line and counter attack. Alas, to late to save the North.


Long story short an interessting way to make the game exciting

Thanks for sharing Espejo, glad to see it was effective in your game and you enjoyed it .
If the Entente do well or CP is unlucky/screw up a bit you can save Belgium or at least force Germans to fight hard for Ypres (as was the case in 1914) if not Antwerp but that's all up to players moves.

[Bavre]

So Dazo and I just played through the beginning moves of his Schlieffenplan.

I am relatively new to SC, so take anything I say on it with a grain of salt and feel free to correct!

Anyway my 2 cents:

Belgium and northern France are doomed unless the Belgians get extremly good combat roles. In our game Dazo could advance so fast, that he could even suckerpunch one english corps as it deployed.
The front stabilized at the Somme around Amiens.

What can the entente do? First thing: get the best english general for your HQ that deploys in france asap. Let the best corps under his command entrench in Amiens. As France operate units to the somme, sacrifice your pre-invested research if necessary. I tried to be a cheapskate and leapfrog some units along my line to extend it north and that backfired horribly!
Get Foch and manually let him command the most important/endangered points, while the lesser guys take care of the rest. Since the germans have better HQs, better troops and at least initially a lot more of them, try to play for time
as much as possible. If at all, counterattack only with troops from secure spots to weaken enemies that are about to attack your weak spots. Killing the odd german corps is definitely not worth endangering your line here. They have a second line, you won't for the first few turns!

Dazo decided to leave Serbia alone (except for turn 1 Belgrade) so Galicia was relatively well defended. Russia might be able to get some results in east Prussia or Silesia during those turns, however I botched that, so I can't really tell.

In Belgium the HQ and maybe the last corps can be evacuated via ship, just make sure to secure the escape route. Leave at least one detachment in Antwerp, its death is a small price to pay for the time it buys you. Some goes for the french Marines you can get via decision.

A few thoughts on the strategic implications of the situation:
As long as germany goes straight into trenches (costs just 200 for them to rush it at max speed), they will have trenches 1 before the entente has amassed enough troops for anything more than just a local counterattack. So germany
is practically guarantied to keep its gains until serious artillery takes the field.
They will also most likely end up in controll of 3-4 fields near Verdun. This is no immediate danger as long as they can only attack with infantery, but since you can't do much about it either until you have artillery, the fate of the mighty fortress will be pretty much decided by who rolls out the big guns first. Unfortunatelly this will most likely be germany, since they already start with arty-tech invested and GB/FR don't really have the funds for research in the frantic first few turns.
On the bright side Serbia is now pretty well dug in and should take a very serious commitment to conquer.
This will somewhat extend the time the Turks are on their own. However the Situation in France is a massive drain on GB and Fr resources, so it shouldn't turn out to be too drastic for Turkey.
Since the german airforce can now recon the eastern half of the channel, the entente should not lay any mines there. They will be discovered and their slot wasted, unless they are willing to mine the field that completely blocks the
channel for both sides.
As a consequence, a bigger flotilla is now needed to secure GB troop transports and to stop german subs from slipping through. However since the western channel can be blockaded reasonably well, I doubt the submarine war would
change too much. Just make sure your blockade is out of recon range for the germans.



In any case the morale effect of it all is quite hefty and I'm not just talking about National Morale [X(]

[1775Cerberus]

ORIGINAL: Bavre
In any case the morale effect of it all is quite hefty and I'm not just talking about National Morale [X(]

That is the morale effect that must be viewed in the long game. Do not give in to the urge to not do anything because you are afraid of losing more units or ground. At the same time do not give into the urge to strike out blindly to "do something" causing you to lose units or ground.

Approach the game as a chess match. There will be times where you will have to sacrifice something or a position to place yourself in a better position for the long game. The long game is national morale. Yours, your allies, and the enemies. EVERYTHING you do should be viewed through that filter.

It has a very historical effect. Are you a "central front" or "periphery" leader? Do you focus on breaking Germany, or do you defeat them by defeating their allies? Once you answer that question, things get much easier. Pick the fulcrum points and know when cost outweighs gains. V. Falkenhayn grasped this truth, then lost sight of it at Verdun.

[Dazo]

Thanks for the review on your side Bavre ,

Lots of good advices to deal with Schlieffen. And you're right about Verdun, Schleffen tends to make it a natural target for future german offensives as it usually ends up being a salient in german lines.
I agree that buying back french starting research should be done if Germans really do well with Schlieffen, just to operate units from the right flank to the left since german advance can't cut all rairoads to Belgium on turn 1.
That's the strength of Schlieffen: only leaving Entente with bad choices to make.

As Bavre says Germans can just play defense from turn 2-3 (except units racing to the sea/dealing with Belgian units) and send extra units to other fronts pretty quickly.
Since I got lucky and captured Belgrade on turn 1 I felt I could leave Serbia alone for some turns to push my advantage in France and push back Russians beyond the border.
Had a lvl 8 german HQ and 4 infantry corps plus lvl 5 AH HQ and 3 infantry corps ready for a push to Nish (german artillery in reserve).

Bavre made some mistakes just because he didn't know well where scripted units would appear (BEF or AH reinforcements in Galicia). He moved one french corps in Amiens which could have been occupied by a BEF corps. That BEF corps appeared south of Amiens and was more vulnerable (german units adjacent). The french corps could have been used to link with Boulogne marine unit and then Belgians, would have made things harder for Germans.

[OldCrowBalthazor]

Dazo,

This is such well done study and guide of the Schlieffen Plan. I commend this effort that you have undertaken to post this. It is clear, concise, and polished. I particularly have enjoyed the maps that you used to illustrate the step by step procedure that needs to be undertaken to make this daunting operation a success.

I have always done a France First strategy in my MP games. I also know that my opponents who are experienced, always do a France First also. There are hazards of stumbling this thing though, especially if Brussels is not captured on the first turn, and other mishaps, but you show the proper sequence to make the opening moves favorable to the Central Powers.

I have found that Central Powers players that forego a France First strategy, will invariably lose the war (and the game).

Anyway, thanks again for this handy work, which even an experienced Central Powers player will find indispensable!

[Chernobyl]

One of my opponents defeated a version of this attack. You can't leave a one-hex supply strip along the Reims diagonal. Because on the first Entente turn, France can kill one of your corps either in Reims or in the hex northeast of Reims, and throw a cavalry unit there, which will cut the supply off every unit west of Reims. They will be at 0 supply and take attrition damage, and will be carved up. (Especially likely to happen if they put their best general to use immediately)

A solution to this is to opt to go for the Loos mine instead of capturing Lille. That way you have a two-hex diagonal supply chain that cannot be broken. It sucks cause this lets them entrench at Lille. One nice thing about this version of the attack is that it forces the British II corps to spawn behind Amiens instead of in front of it, which affords you a bit more wiggle room. I've found it's just barely possible to defeat Belgium, capture Lille, and defend from French and British counterattacks. You may trade corps back and forth until French NM falls below 95% and (more importantly) you get your first entrenchment tech.

You need to put the strongest unit you can in Reims. A half cross experience unit won't do. But a full star unit makes it likely to survive a determined attack. The two cavalry in the swamp actually shield the corps in Reims somewhat which is nice. And as an added bonus the swamp cavalry actually threaten Paris and prevent a HQ from walking into Paris. So although he gets a free detachment due to your attack, he has to leave some unit defending Paris which prevents the French player from deploying his units most aggressively and marching/railing into Belgium quite so much.

[Chernobyl]

I'm also confused how you get an infantry unit north of Brussels without sacrificing any cavalry movement on an attack. My two infantry ALWAYS go dark after attacking Brussels. They never ever have an extra movement point left after they attack, even when they had 1 movement point remaining as they attacked.

[Chernobyl]

I do disagree about not attacking in the south though. It's worth killing the most vulnerable French corps there. Just kill one guy. It helps a few turns later when the French would love one extra attacker to pressure you from the south. And you say you're not there to bleed France, well then I think you're missing the point of attacking Belgium. A battle in the west prevents France from rapidly teching up. Every MPP they spend on repair and replacement is lost tech money. Overall you should do more damage to the French than they do to you. Your units are stronger so the casualties should favor you. And then you eventually take Verdun, which lowers their NM significantly and starts draining it every turn. Every French corps you kill hurts their NM further and things snowball. You want France reaching critical NM levels before the Ottomans bottom out and it's quite doable.

Not to mention the more corps you kill the more HQ experience you get, which is another snowball effect that greatly helps you in the long run!

Also another detail: one unfortunate downside of attacking Belgium is that France will get "increases arms production in the southwest" activating some powerful mines. I believe the events are triggered when you capture Belgian and French mines near Lille and Brussels. So you're not gaining quite as much of an MPP advantage as you might believe. Still worth it to attack in the west though, imo.

[Dazo]

Hi Chernobyl, thanks for the comments on Schlieffen .

ORIGINAL: Chernobyl

I'm also confused how you get an infantry unit north of Brussels without sacrificing any cavalry movement on an attack. My two infantry ALWAYS go dark after attacking Brussels. They never ever have an extra movement point left after they attack, even when they had 1 movement point remaining as they attacked.

The corps ending north of Bruxelles should be the one starting in Aachen.
It needs 1 AP to go through Lieges then 1 AP to be adjacent to Bruxelles + 1AP because of the Belgian corps ZoC.
So it should have 1 remaining AP before attacking, that AP should be available after attack to advance north of Bruxelles;
(but only if the Belgian corps in Bruxelles fell under 5 steps, disabling its ZoCs)

The problem I can see is that you capture Lieges with the Aachen corps which cost 2 AP instead of 1.
To avoid that, you should capture Lieges with another unit than the Aachen corps after destroying the Belgian detachment.
(see section III of part II from the study, move number 3)

ORIGINAL: Chernobyl

I do disagree about not attacking in the south though. It's worth killing the most vulnerable French corps there. Just kill one guy. It helps a few turns later when the French would love one extra attacker to pressure you from the south. And you say you're not there to bleed France, well then I think you're missing the point of attacking Belgium. A battle in the west prevents France from rapidly teching up. Every MPP they spend on repair and replacement is lost tech money. Overall you should do more damage to the French than they do to you. Your units are stronger so the casualties should favor you. And then you eventually take Verdun, which lowers their NM significantly and starts draining it every turn. Every French corps you kill hurts their NM further and things snowball. You want France reaching critical NM levels before the Ottomans bottom out and it's quite doable.

Not to mention the more corps you kill the more HQ experience you get, which is another snowball effect that greatly helps you in the long run!

Also another detail: one unfortunate downside of attacking Belgium is that France will get "increases arms production in the southwest" activating some powerful mines. I believe the events are triggered when you capture Belgian and French mines near Lille and Brussels. So you're not gaining quite as much of an MPP advantage as you might believe. Still worth it to attack in the west though, imo.

I believe there are some misunderstandings here:

1) I'm not saying not attacking at all, you should if you have good odds but I just hold the line and don't try to advance because I need ressources in other places.
However priority on turn 1 is to grab free hexes and entrench because you'll then be able to attack without worrying too much about french counterattacks.
If you go all out there, you may cripple France but Russia may also take advantage of it and become a very big problem.

2) The objective isn't to bleed France in the southern part of the front (Part II, section II, note 1), as you say it's the point/objective of the attack on Belgium which means the northern part of the advance. Unless you mean Belgium as "the West" but in that case it's not about Schlieffen anymore, it's another strategy entirely.
Bleeding France is Verdun style strategy while Schlieffen expected more of a 1871 war outcome with victory by maneuvering instead of a frontal offensive against the bulk of french forces.

3) I also stated that Schlieffen has many variants and the one I studied is just one of them though quite close to history.
As said in the study, it isn't any surefire plan to win and you have to adapt (depending on your plans, tastes, style or whatever). You're free to prefer other moves and do it your way of course [8D].

The point about french mines in the south can be found in page 2 of the study, Part I, Pros 2), comment under MPPs numbers ^^ .


As a conclusion, I'd say the main goal of that study was to make players who avoid attacking Belgium think about it which should align with your strategic views about neutralizing France first even if the follow up and execution vary.

[Dazo]

ORIGINAL: Chernobyl

One of my opponents defeated a version of this attack. You can't leave a one-hex supply strip along the Reims diagonal. Because on the first Entente turn, France can kill one of your corps either in Reims or in the hex northeast of Reims, and throw a cavalry unit there, which will cut the supply off every unit west of Reims. They will be at 0 supply and take attrition damage, and will be carved up. (Especially likely to happen if they put their best general to use immediately)

A solution to this is to opt to go for the Loos mine instead of capturing Lille. That way you have a two-hex diagonal supply chain that cannot be broken. It sucks cause this lets them entrench at Lille. One nice thing about this version of the attack is that it forces the British II corps to spawn behind Amiens instead of in front of it, which affords you a bit more wiggle room. I've found it's just barely possible to defeat Belgium, capture Lille, and defend from French and British counterattacks. You may trade corps back and forth until French NM falls below 95% and (more importantly) you get your first entrenchment tech.

You need to put the strongest unit you can in Reims. A half cross experience unit won't do. But a full star unit makes it likely to survive a determined attack. The two cavalry in the swamp actually shield the corps in Reims somewhat which is nice. And as an added bonus the swamp cavalry actually threaten Paris and prevent a HQ from walking into Paris. So although he gets a free detachment due to your attack, he has to leave some unit defending Paris which prevents the French player from deploying his units most aggressively and marching/railing into Belgium quite so much.

As stated in the study, there are ways to counter Schlieffen but there is no easy way, it's give and take.
Plus what you consider defeating the attack doesn't necessarily match what other players would consider to be a defeat.
(depends on your objectives and what casualties you're willing to take to achieve them)

The move to take Loos mines instead of Lille is covered in the study Part II, section V, attack sequence point 5).
It's one of the choices you have to make as Germans. There are pros and cons, taking Lille is only my preference.

Anyway, no harm talking about it .

It's hard for me to picture what happened with just words especially when you say "a version" of that attack.
Even with the same moves, combat rolls can bring different results so even one move change can mess up the whole process and that's also in the study. Things are different depending on the hex captured (Reims or the one NE of it).
Reims isn't that easy to take as you say.

You could entrench the cav with elite step and not forcemarched in Reims (move talked about in the study) which make it very hard to kill on turn 2.

The forcemarched corps NE of it may be more vulnerable but France would need at least 3 attacks to kill it (with some casualties to boot if Germans attach that corps to von Kluck which should be an experienced lvl 7 HQ at tate time) and advancing a cavalry there means it will get massacred next turn by Germans with few losses.

0 supply:
Plus even if you do that, I'm not sure how units closest to Paris got 0 supply.
If I'm not mistaken, Reims and Mons mines should be CP controlled which should cancel the location ZoC from Loos mines the next turn while you have more units surrounding the rail hex north of Reims than France (should also work for the hill hex of Chemin des Dames NW of Reims).
So at the start of turn 2, that rail hex should become CP controlled meaning you have a supply path to advanced units.
Forcemarching the french detachment in Paris to Loos mines may help counter that but that's just another massacre in the making.

Even if those advanced units are at 0 supply, it doesn't matter much because they can still entrench and their goal is to gain time while disrupting french moves towards Belgium (that's mission accomplished if France uses its manpower around Reims).
Sure it can be a pain to lose some corps (even including 1 or 2 in low supply) but I find it acceptable if it helps clear Belgium fast enough.

Isolated units should get back in supply when Germans counterattack the french counterattack (french units should be reduced and/or unentrenched) and Germans only need to regain 1 hex which they can certainty do. France shouldn't be able to destroy them in such a short time and Germans still have the option to retreat to a shorter line.

In the end, that's what make Schlieffen a great opening: each side has chances to make interesting moves instead of just slugging it out in Alsace-Lorraine.

[Chernobyl]

ORIGINAL: Dazo
The corps ending north of Bruxelles should be the one starting in Aachen.
It needs 1 AP to go through Lieges then 1 AP to be adjacent to Bruxelles + 1AP because of the Belgian corps ZoC.
So it should have 1 remaining AP before attacking, that AP should be available after attack to advance north of Bruxelles;
(but only if the Belgian corps in Bruxelles fell under 5 steps, disabling its ZoCs)

I agree with everything you say until "that AP should be available..."
Because every single time I attack, it loses its last movement point. Zero remain. Every time. I've never been able, even once, to use the last movement point. It isn't a matter of ZOC. The attack on the Belgian corps takes it down from 1 to 0 and the unit goes dark. No, I'm not showing up with zero remaining. I do put a unit inside the Liege fort to get the max out of my movement points. It just doesn't work for me. How you get consistently different results I have no clue.

[Chernobyl]

ORIGINAL: Dazo
combat rolls can bring different results so even one move change can mess up the whole process and that's also in the study. Things are different depending on the hex captured (Reims or the one NE of it).
Reims isn't that easy to take as you say.

Try it out yourself. Attach the best French general and crash into Reims. Throw the cavalry unit there and your guys will be out of supply. It's not that difficult to do.

[Dazo]

Hi Chernobyl ,

ORIGINAL: Chernobyl
I agree with everything you say until "that AP should be available..."
Because every single time I attack, it loses its last movement point. Zero remain. Every time. I've never been able, even once, to use the last movement point. It isn't a matter of ZOC. The attack on the Belgian corps takes it down from 1 to 0 and the unit goes dark. No, I'm not showing up with zero remaining. I do put a unit inside the Liege fort to get the max out of my movement points. It just doesn't work for me. How you get consistently different results I have no clue.

That's weird, I can do it most of the time and other players like Espejo managed to do it too.
The loss of AP can happen but souldn't happen every time.
It's like the cavalry move towards Lille, the cavalry corps could actually stop near Bruxelles and try to finish the belgian corps but I usually don't do it because there is a chance it will lose its last AP in that combat and can't reach Lille.

Did you attack Bruxelles with another corps before attacking with the Aachen corps ?
Was Bruxelles corps below 5 steps after the Aachen corps attack ?

As I said, it's hard to understand what happened with just words... Maybe just very bad luck but who knows.

Anyway, not the end of the world even if you can't take that rail hex north of the city.
UK will have to spend MPPs to operate the Bruxelles corps out to save it on turn 1 and that corps will be in bad shape.

ORIGINAL: Chernobyl
Try it out yourself. Attach the best French general and crash into Reims. Throw the cavalry unit there and your guys will be out of supply. It's not that difficult to do.

I did (hotseat) and that's why I said what I said.
Reims isn't easy to take with one cav covering it in the southern hex and that's what you said too.
But in the game you talked about with another version of Schlieffen it was about the hex NE to Reims so excuse me but your words are a bit confusing, maybe a screenshot would help a bit.
If Reims is taken, yeah supply should go to 0 for advanced units but they can still entrench and wait for German counterattack on turn 2 as said above (after which they should be able to regain supply and be reattached to HQs, attrition or not).

Anyway, sure, one of those two hexes can be taken but that's part of the game, you take a risk with forcemarch.
At worst, you'll lose some units and german front will be shorter, can happen.

If you want, I can start a MP game with this opening and we can just play some turns in the West to see the possible moves.
(sorry but I'm not able to play another full game for now)