I don’t know what it is but it has been popping up everywhere as of late. I exclusively play the Queens Gambit and there are many more popular responses to it but it seems to have caught on in blitz. It could be the general ELO of the opponents is higher I play now and I can see why the Tarrasch would be difficult for White to play against without some idea of what to do. In a 3 minute game you don’t have time to figure out an entire opening on the fly like a rapid or classical game. Let take a look at what the Semi-Tarrasch opening is. This is our starting position for all the analysis ahead.
What Black wants to do is trade their c pawn for White’s d pawn or if White captures on c5 Black will recapture with the bishop of f8 while developing. It’s understand able for Black to play, generally one way or the other Black gets to trade his wing pawn for a center pawn but at what cost? Well, it depends on how White response in this position since there are 4 decent ways to recapture each leading to it’s own feel. You’ll have to do some visulization here but it’s good for practice. These line are in the game analysis which I post at the bottom where you can see them on the board.
The most common is 1.cxd5 Nxd5 2.e4 Nxc4 3.bxc3 cxd4 4.cxd4 Bb4+ 5.Bd2 Bxd2+ 6Qxd2. What we get after this position is a simplifed game, two minors have been swapped off already. Black’s upside is the lead in development since they are already castled they can begin attacking the center earlier while While has to develop the light bishop and castle.
Next White opts to keep the tension by not capturing at all 1.e3 Nc6 2.a3 a6 3.dxc5 Bxc5 4.b4 Ba7. Here White captures and allows the bishop to develop but immediately kicks the bishop back with b4 gaining space and time. White has a lot of options on how the want to proceed, some people continue to attack and push on the Queen side while others will finish developing and castle.
3rd most common is 1. Bg5 which is following in the classical feel of the Queen’s Gambit declined where you get the bishop outside the pawn chain before e3 is play. 1…cxd4 2.Nxd4 e5 3.Nf3 d4 4.Bxf6. This gets complicated very quickly, if sharp positions are something you favor this would be a great continuation for you.
Lastly is what I have been playing lately and experimenting with 1.dxc5 Bxc5 2.e3 O-O 4.cxd5 exd5 5.Be2 which tends to become a very typical style game. The major upside is Blacks isolated pawn which will become a target later in the game but as a whole the position is balanced.
Of these four I would choose 1.e3 and 1.dxc5 as my options based on how I like to play. Both of them turn into relatively stanard openings but White still keeps a small edge in some way. The game continues equally until Black get tunnel vision on a checkmate and misses an intermezzo capture with check which forces them to change plans.