When can and should i play the trompowsky?

I tried to learn the trompowsky recently but many times i couldnt get it because of 1.d4 e6 and 2.Bg5 would be just a blunder. I also hear its unsound(but playable) after 1d4 d5 so i consider learning a line in the queens gambit from Kornevs book to fill this hole. I dont have any preferences but i like to know that i play sound lines and not depend on to Much suprisevalue. Is there more situations where i should leave out the trompowsky?

The "when" is after 1.. Nf6. After 1.. d5 it can transpose to the Trompowsky, but only if your opponent plays Nf6 after.

All the time and very carefully....and with a hella early h4........

1. d4 Nf6 2. Bg5 is the Trompowsky. 

1. d4 d5 2. Bg5 is like the Trompowsky, a sort of pseudo Trompowsky. Not as strong as the Trompowsky, but not a joke. 

Neither of the openings give away anything, so personally I wouldn't use the word "unsound". 

I believe they are both better than 2. b3 or something like that. I am unsure how the pseudo Trompowsky compares to the Richter-Veresov.  

Do not try and play the Trompowsky after you open 1. e4.

This is known as the Levitsky attack  ( queens bishop attack ) 

It think that's called the Teleporting Bishop attack.

They're okay if you want to avoid learning tons of theory, but nothing that you should rely exclusively on.  The d4-Bg5 idea also works well against the Dutch Defense, where it's actually causing significant problems if I remember correctly.  However, against other Black moves such as e6 and d6 it doesn't quite work, so you'll need something prepared against them if you want to play d4-Bg5 a lot.

I just like the positions from the trompowsky:) its really not a theorysaver anymore. I think i will play Kornevs Lines from his 1.d4 mainline books against 1.d4 d5 and 1...d6, trompowsky against the rest and we will see how it goes

When you can? Whenever you want. When you should? Never!

When Black plays ...e6 with the idea of ...d5 or ...f5 you won't be able to use the trompowsky. You could try something like the Jobava attack which includes d4, Nc3 and Bf4. There isn't much theory on it since he just made it up and it's already usable as an anti-Dutch line as well. And there's always 2.e4. 

i will assume from your comment that you are a 1.e4 player after looking at your rating. g5 is possibly the best square for the bishop for 1.d4 players so the trompowsky is better than the usual d4 sideline. in the mainline queens gambit it also goes to g5, same for the semislav, samisch  variation, averbach kid and that is mainlines. against 1.d4 f5 2.Bg5 its so tricky that 1.d4 f5 specialist gm simon williams start with 1...e6 to avoid this spesific line. the trompowsky has also seen a resurrection on masterlevel+ lately and is getting alot of coverage on chesspublishing.com and its scoring well

thank you for nice suggestions guys! im following richard perts very nice book on the trompowsky. it covers it nicely and even covers 1.d4 d5 Bg5 saying its probably unsound but gives interestning games where white is about equal. my recent "problem" now is black playing similar to this

and i see nothing better than to transpose to a mainline kid samisch or averbach if i want to justify a bishop on g5 unless there is some interestning line or moveorder i dont know about. i probably dont want to learn another sideline as after 1.d4 the trompowsky is the only sideline i like. i guess i just have to learn both the trompowsky and the mainline kid. in that case there is a chance i put away the trompowsky and play only mainlines after 1.d4 as i dont like londonsystem, colles and such

The Drevland - a common mistake players make is that they think that these "systems" with 1.d4 are playable against everything, and they aren't.  You need to mix and match.

For Example:

Playing 2.Bg5 - Against 1...d5, it's very risky.  Against 1...Nf6, you have the Trompowsky, a respectable opening.  Against 1...f5, you have a fairly popular line of the Anti-Dutch.  Against other moves, like the Modern (1...g6), it's just bad.  Too early to commit.  After 1...g6, you need to play 2.e4 or 2.c4.

Playing Bf4, Nf3, and e3 in some order - This is known as the London System.  It also is HORRIBLE against the Modern Defense (i.e. 1.d4 g6 2.Nf3 Bg7 3.Bf4?! d6 4.e3 Nc6 5.h3 e5 advantage Black!

Playing the Colle (Nf3 and e3) is not very good against systems where Black fianchettos his King's Bishop, like 1.d4 Nf6 2.Nf3 g6 3.e3?!.  It is best played when Black commits to d5 and preferaby e6, like 1.d4 d5 2.Nf3 e6 3.e3!, otherwise, you get Anti-Colle systems with ...Bg4

The Torre Attack only works against Nf6 and either g6 or e6, like 1.d4 Nf6 2.Nf3 g6 3.Bg5 or 1.d4 Nf6 2.Nf3 e6 3.Bg5.  It's no good against Nf6 and d5 because of 1.d4 Nf6 2.Nf3 d5 3.Bg5?! Ne4! with full equality already, if not even a slight advantage for Black!

The Veresov (1.d4 and 2.Nc3) fails to work against the Modern (You end up in a Transposition to the Modern Defense, so not fails in terms of losing, but you can't stay in Veresov Territory, you are now in Modern Territory) and the Benoni (1.d4 c5 2.Nc3?! cxd4 3.Qxd4 and Black can already harass the Queen.)

TheDrevland wrote:you should play it every time after d4, Nc3, then Bg5

I tried to learn the trompowsky recently but many times i couldnt get it because of 1.d4 e6 and 2.Bg5 would be just a blunder. I also hear its unsound(but playable) after 1d4 d5 so i consider learning a line in the queens gambit from Kornevs book to fill this hole. I dont have any preferences but i like to know that i play sound lines and not depend on to Much suprisevalue. Is there more situations where i should leave out the trompowsky?