1. d4?! concedes 15 centipawns advantage or so; 1. c4! is better
1...Nf6?! concedes 20 centipawns or so; 1...c5! is better
2. Nc3? concedes 30 centipawns or so; 2. c4 is obviously better
No way, c4 will get you in the Hedgehog, which is deadly if you play wrongly
https://www.chess.com/forum/view/chess-openings/jobava-london-system#comment-42811050
All this Jobava/Mark talk, let's not leave Barry out!
After something like 3...e6 4.Nb5, yes, you have the Jobava Attack, along with many other lines, but if Black plays 3...g6, then 4.Nf3 would be the Barry Attack, not the Jobava Attack. 1.d4 Nf6 2.Nc3 d5 3.Bf4 g6 4.Nf3 is the same thing as 1.d4 Nf6 2.Nf3 g6 3.Nc3 d5 4.Bf4, the more traditional way of reaching the Barry Attack.
Come on guys. This is about the opening itself not the name, mark attack, jobava Attack or Barry. To be honest, it looks like Veresov or the chigorin little to me..........I do not have any sources for the Jobova, but I would suggest u look into the different opening that your opponent can commonly do, and work from there
Introduction To The London System & Jobava London System...
https://www.chess.com/blog/RussBell/the-london-system
https://www.chess.com/blog/2Bf41-0/3-reasons-why-everyone-should-play-london-system-pawn-structures
And the following 3 blogs actually discuss the Barry/Jobava-Prie` Variation.
https://www.chess.com/blog/2Bf41-0/poisoning-the-grunfeld-with-the-london-part-three
https://www.chess.com/blog/2Bf41-0/poisoning-the-grunfeld-with-the-london-part-two
https://www.chess.com/blog/2Bf41-0/poisoning-the-grunfeld-with-the-london-part-one
just youtube search GM Chess Lessons London System and get the one that says GM Chess Lessons London Systems. There you will find about 5 videos with good games to use as a template. It even shows how to combat the Nh5 idea in some cases.
Hey, thanks for the response! However, I don't see the video labeled " GM Chess Lessons London System." Would you happen to have the link?
I can't seem to find the videos anymore. They must have been taken down, however, if you type in London System Part 1 you will find tons of different series of videos on the london System.
You can play either or in the London System. It doesn't matter. Take your pick. The doubled pawns aren't really that bad, and sometimes can help you, and, losing the bishop isn't that big of a deal. The Knights will play a big role in future moves if you play the London System correctly. Just remember to try and do things with your knights, once your London bishop gets traded. There is another tactic to know much later on in the game when Nh5 is played, however, I forgot the tactic. Your best bet is to hope that those videos you find on the London System will show you that tactic. I didn't make a pgn of the games because I don't like the London System and didn't want to bother. I wish I had more info, but alas, I do not care about the London System, sorry 
.
3...Nh5 is nonsense; no wonder you can't find anything. A simple Be5 works, leaving black in a pretty stupid position.
Agreed. For example, White missed a mate-in-1 on move 13 in this game:
https://www.365chess.com/opening.php?m=8&n=23399&ms=d4.d5.Nc3.Nf6.Bf4.Nh5.Be5&ns=7.8.80.55.4507.39079.23399#
3...Nh5 is nonsense; no wonder you can't find anything. A simple Be5 works, leaving black in a pretty stupid position.
Agreed. For example, White missed a mate-in-1 on move 13 in this game:
https://www.365chess.com/opening.php?m=8&n=23399&ms=d4.d5.Nc3.Nf6.Bf4.Nh5.Be5&ns=7.8.80.55.4507.39079.23399#
I am unable to open the link. Does there exist anyone else who cannot do so?
This forum probably blocks PHP shell commands.Try this, and click on the 4. … f6 move:
Come on guys. This is about the opening itself not the name, mark attack, jobava Attack or Barry. To be honest, it looks like Veresov or the chigorin little to me..........I do not have any sources for the Jobova, but I would suggest u look into the different opening that your opponent can commonly do, and work from there
Its all London to them. Its part of being "agile".
Just to refresh (some need it it seems) :
Barry attack : only on g6, with the idea to continue e4 and transpose into a Pirc if black allows it. SO d5 now and so on, when white has several plans.
Veresov, with Nc3-Bg5
Jobava (Prié) Attack. Can transpose (rarely) intro Barry attack if black plays with g6 , but white can use this move order to play f3 instead of Nf3 in some variations.
While London system is defined by 1.d4, Nf3, Bf4 (or Bf4 before Nf3), when white rarely continue with Nc3 but c3 or even c4.
These openings are cousins, but lead to different play and move order is very important.
Is "London system" a generic name for calling various yet unrelated d4 lines different from the queen's gambit?
Come on guys. This is about the opening itself not the name, mark attack, jobava Attack or Barry. To be honest, it looks like Veresov or the chigorin little to me..........I do not have any sources for the Jobova, but I would suggest u look into the different opening that your opponent can commonly do, and work from there
Problem is it is not just about a name. The London, Jobava, and Barry all have completely different ideas. The London is all about avoiding all weaknesses, like doubled pawns, at the cost of space and leading to mere equality. It entails a gradual attack by White on the Queenside.
The Jobava is a rapid attack for control of c6 and the h2-b8 diagonal as a whole (4.Nb5 is common). That diagonal is weakened by d7-d5.
The Barry attack involves g6 having been played by Black combined with d5. After 1.d4 Nf6 2.Nf3 g6, the move 3.Nc3 threatens e4, heading for a Pirc. If a Grunfeld or KID player wants to avoid it, 3...d5 is the only way, which KID players loathe. Now 4.Bf4 with that weakened diagonal, and now, unlike the London, White almost never castles kingside, usually queenside or not at all, plays an early h4 and goes for a direct shot on the kingside.
They truly are different openings that can transpose into one another and you need to be aware of such things. And yet, despite Nc3 played, these are all vastly different than the Veresov!
Many amateurs think you can cherry pick a single QP system without c4 and succeed. Wrong!
Torre is no good vs 1...d5 or 2...d5
London is no good vs the Modern
Colle is no good vs Fianchetto Defenses or lines withou ...e6. The anti-colle with Bf5 or Bg4 must be answered by c4, leading to the slow slav
Veresov can't be played vs the Modern Defense or Benoni Lines (1...c5 or 2...c5)
And the list goes on. You have to group these lines together like Summerscale does in A Killer Chess Opening Repertoire, for example, or for a while I played the Torre vs Nf6/g6 and Nf6/e6 and the Colle or Slow Slav vs early d5 lines, etc.
I would just play 1. d4 ...Nf6 2. Nc3 ...d5 3, Bf4 ...e6 as black. White's moves place no real pressure on the centre. The quickest way to create an imbalance is to close my c8 bishop in since white did the opposite. Then just outplay the opponent, if I'm playing well, that is.
You have to group these lines together like Summerscale does in A Killer Chess Opening Repertoire, for example, or for a while I played the Torre vs Nf6/g6 and Nf6/e6 and the Colle or Slow Slav vs early d5 lines, etc.
That's it! In my london system ressources white starts with 1. d4 d5 (or 1... Nf6) 2. Bf4, but sometimes plays c2-c4 or Nc3 (with the pawn still on c2). The f1 bishop also has squares on e2, d3 or b5. Sometimes it's good to capture on c5, and so on. Everything depends on what black does.
Jobava and barry attacks and some slav variations are also part in the already mentioned book "The agile london system" by romero and de prado. In one other ressource there is a transposition into a caro-kann
1. d4 d5 2. Bf4 c5 3. e3 cxd4 4. exd4
1. e4 c6 2. d4 d5 3. exd5 cxd5 4. Bf4
So the name of this variation must be the london exchange caro-kann? 
Is "London system" a generic name for calling various yet unrelated d4 lines different from the queen's gambit?
Not as far as I know. The London system is 1 d4 2 Nf3 3 Bf4. It's got nothing to do with Mark's Opening, and as far as I know it's got nothing to with the Barry attack or Veresov Attack either.
So the name of this variation must be the london exchange caro-kann?
Yes. However it can get complicated. Black to move..is this London... or Jobava London?
The London expert will know the answer: its Jobava as white is 2 moves down because Jobava.
The Jobava London looks very much like what we've always called The Barry Attack.
https://en.wikipedia.org/wiki/Barry_Attack