Deleted member 1487
What if von Kluck's 1st army had managed to chase down the BEF and crush it after Mons? What would the effects have been on the later battle of the Marne and the political situation in Britain?
I found the perfect POD for this idea. Turns out Sewell Tyng talks about this in his book on the Marne. Von Beloew of the 2nd army ordered von Kluck to conform the 1st army to his flank at the battle of the Sambre. Von Kluck wanted to swing further West first, which would have left him to the West of the BEF at Mons. Tyng suggests that had this happened then the BEF would have been encircled and destroyed in its very first engagement. So let's say that happens.
The BEF is taken in the flank and surrounded as the French 5th army retreats. The 1st and 2nd corps are destroyed along with most of the British cavalry. This is a major hit to morale and the British now only have the 3rd and 4th corps, both of which were understrength as it was. How do the British react and what happens during the rest of the campaign? The French 5th army can only really retreat, because every time it stops to fight, von Kluck with charge his flank. This also leaves a major gap in the line that the French 6th army will need to fill, as will extra troops taken from the frontier to cover Paris. The British are unlikely to commit more troops to the continent, as their morale is likely very shaken thanks to the first engagement in nearly a century in Western Europe ends with their army being wiped out.
Allenby's cavalry and the nascent RFC did a superb job of scouting and screening for the BEF. They won the information war. French committed the BEF at Mons because he knew where the Germans were, and did it again at Le Cateau. Le Cateau wouldn't have been near as worrying to the BEF if Haig hadn't panicked and not put the 2nd Corp into action on the 1st's right flank like he was supposed to.
Finally, you can retreat faster than you can advance, and Robertson did a brilliant job as QMG in setting up supply dumps along the path the BEF had to retreat along.
For the Germans to trap and destroy them they need to do two things. The first is to work out how to shoot down opposition aircraft, and the second is to somehow trap and destroy the Cavalry Brigade. They proved singularly inept at both during the Retreat to the Marne.
3rd and 4th Corps? I thought the BEF was only about 6 divisions strong during these first few weeks of the war.
Consequently, by about mid-September Moltke would succeed in pincing off Verdun and 2nd French Army.
I think you mean the French Third Army.