Well, first off - it's quite possible, so long as Lee's forces are much better trained than they were OTL. (The training quality in the ACW was not very good, especially in the beginning.)
One way to do it would be a properly pressed bayonet assault late on (once all the Union troops have been committed to the battle - say it's Penders' and Fields' brigades who make the assault or some equivalent, done the "Napoleon way".) It's a gamble, but I think it's one we can (for the sake of argument) assume to be successful.
Now, as to the question of recognition.
Recognition does not equal military support - let's make that clear first.
We know from other situations that it was rare for the British to recognize someone before they'd unambiguously won their freedom, and it's possible the CSA could languish unrecognized despite such a victory as this...
...but what this victory does do is give the Union severe problems. No matter the scale of the casualties Lee's force has taken, it's just caused a huge morale blow to the trained manpower of the Union and put them on the defensive in a big way.
Perhaps more importantly, though, it demonstrates that Lee's method of fighting (this ATL one which has won the victory) is the right one. This is quite a correct assessment, and probably leads to the CSA winning further victories at least until the Union can copy it... and it also fundamentally changes the character of the Civil War, since it now means major "decisive" attacks can be made with reasionable confidence.
(OTL only a very few bayonet assaults succeeded.)
This pretty much upends the nature of the whole war and it's hard to say what happens.
...though perhaps we should instead say that the PoD is better French support in the first place, perhaps a few NCOs "unofficially" going over, because the French method of attack absolutely was to do a balls-out bayonet charge right through the firing area of defending riflemen! It worked wonders when fighting the Austrians.
(They didn't change to fire-based combat until the Austro-Prussian War of 1866.)
In case you're wondering, yes, bayonet charges are not rendered impossible by rifles or 12-lber Napoleons. They're not even rendered obsolete by machine guns and magazine rifles, or even assault rifles, since the British took many positions with the bayonet in the 1982 Falklands war and since the Japanese accomplished bayonet charges in the Russo-Japanese War in 1905. 1865 is far too early for technology to have rendered a bayonet charge impossible.
I'm pretty sure the quality of force has to be right. I mean, that's kind of what I'm suggesting should be different - it's not as if the Army of the Potomac at Gettysburg had more killing power over the last hundred (or fifty!) yards than the Russian defenders with their magazine rifles in Manchuria. After all, the Army of the Potomac only had about one shot every twenty seconds.In the OTL battle, Little Mac had two Corps in reserve. With the correlation of forces it is virtually impossible for the Confederates to commit all of the Army of the Potomac in the battle, let alone with a general as determined not to commit troops as MacClellan leading it.
Bayonet charges have also been used in Afghanistan, again by the British. Totally not impossible, but the situation has to be right, otherwise you get Pickett's charge.
I'm pretty sure the quality of force has to be right. I mean, that's kind of what I'm suggesting should be different - it's not as if the Army of the Potomac at Gettysburg had more killing power over the last hundred (or fifty!) yards than the Russian defenders with their magazine rifles in Manchuria. After all, the Army of the Potomac only had about one shot every twenty seconds.
And - out of curiosity - which corps were those held in reserve?
Well, the point I was making was largely that the firepower of the Army of the Potomac was not sufficient to stop a well trained force - but of course it did stop Pickett, because the charge was not pressed by high enough quality infantry.The AotP did for Pickett...
IIRC (I'm away from my books right now), V and VI Corps
I'm a firm believer that special order 191 was a ruse, designed specifically to get McClellan to use his army. It's really, really hard to defeat an army that is not allowed to come out and play.
Exactly as the title says, let's say Mclallen screws up big time.
mauling = 40%+ dead and Union army withdraws from Maryland.
How would the ACW look after that, would the Brits and French recognise the confederacy.
the alternative (SO191 stays safely tucked away or unwritten), per the theory is that Lee would be exposed, and unable to find a place of respite without exposing Richmond, and more likely to have to do battle in a more unfavorable site. IF there had been no ruse, and no lost orders, it could have been far worse for the south.
you tell me, what did Lee lose by losing the order? he wasn't on his way anywhere other than trying to find a place to rest. where does he rest? how does he get there? what are his alternatives?
And what precisely did he gain by "luring" McClellan to battle? His army was spread out across Maryland and the valley as it was attempting to cover his rear while he invaded the state to pillage it for supplies. McClellan being anemic and groping around blindly for Lee's army is perfect. He's too timid to leave Washington unguarded (and Lincoln would never allow the AotP to leave Washington unshielded while Lee is somewhere on the flank) and he believes he's outnumbered.
McClellan making an aggressive pursuit is the opposite of what Lee wants. Looking like a fool is so much the better.
Hard to do much "mauling" when Lee was:
1) outnumbered almost 2-1 (87,000 in the field with the Army of the Potomac vs. 45,000 with the Army of Northern Virginia);
2) on the defensive, and still suffering almost as many casualties (~10,000 vs ~13,000) as the US forces on the offensive;
3) suffering from both significant straggling/desertion (the US had substantial forces in the theater that were still unengaged, the rebels did not);
4) suffering from abysmal supply lines compared to the US; and
5) facing McClellan, who as a general officer was the definition of cautiously prudent or prudently cautious.
Other than that, it's a brilliant ... Oh hell, who am I kidding?
As far as recognition goes, the British and French had far too much good sense than to get involved in a losing bet.
Best,