Introduction

Blackmar-Diemer Gambit in my honest opinion is one of the most exciting gambit in chess ever!

It gives you an agressive and sharp position. It is a pure gambit, white don't want to win back a pawn, but instead have something for that. Sometimes you will have the initiative, sometimes an attack, sometimes better coordination of the pieces, and sometime...well...nothing :D But don't worry, in order to achieve that, black will have to give up his material advantage (which is a pawn of course). Yes there are some secret lines in which black can even be more ambitious and try to keep his advantage and proove that our lovely gambit is unsound. About that I will write at the end of theoretical part.

My adventure with that exciting opening started right after my come back in chess. As a small kid I played chess with big interest, winning prizes and tournaments. But life has written different scenario for me and I had to start working and then at the studies I lost interest of that game. I know I know, you will crucify me later...After straight 10 years of my absence I got reemission of diesese called chess. I started to play again, but I needed to reinvent chess from the beginning. So I did abondon The Queen's Gambit, because I knew it inside out, and I thought why after 1.d4 d5 don't play e4! My primary idea was to just give up that central pawn and have some benefits like there is no pawn protecting c4. Then I could put my bishop on c4, which will have a great scope, expecially attacking f7 pawn. I even found one game between two chess programs with that idea. Spoiler alert: white wins :) 

At the end I made an immediate research about my unusual idea of 2 e4 and it turned out it has been invented before. Well quite some time ago...something like 100 years. Why everything in chess has been invented? I could be a pioneer in something.

Anyway, at the end of XIX century english player named Blackmar got an idea the after 

1d4 d5

2e4 dxe4

3f3 exf3

4Nxf3 white not only have better development of his pieces, but also great possibilities by having a half opened f-file. At that time I didn't know about that pattern (giving up two pawns one by one in order to have better development), but it is a well known one. It appears in Benoni (Benko Bambit), against Dutch Defence  (Lisitsyn Gambit), against Bird (1f4 e5 2fxe3 d6). Although in Benoni black is not attacking the king, so there is not that much fun. Practice prooved  that Blackmar was right. It didn't take that long to people to produce a strong answer to his idea. That answer was early e5. with that early counter strike in the center white has problematic position, because taking on e5 is out of the question - no one want to sacrifice a pawn and then attack without his queen (if there is attack for white now).

Fortunate for us in the middle of XX century Emil Diemer made a huge work on that gambit. Instead of playing immediate f3 he proposed Nc3 first. Here I should mention that Bg5, attacking the knight on f6, was never my choice. Propably because white is trying to take back his gambited pawn. We all know that a gambit is not about trying to recapturing it, but having something for it. Expecially in Blackmar-Diemer Gambit. So Nc3 came as an improvement from Mr. Diemer and I have to say that it has more psychological value than scientific one. Now again e5 (Lemberger Counter-Gambit) is a great response...wow my introduction is more pushing than encouraging from Blackmar-Diemer. But it is true, as a chess player I always wanted to seek for the truth, is it sounded or not. Although here I have also prepared one exciting answer for that e5 move - Qh5. Only with that move white can maintain all potential and life in the position. Here is a thing black has to be super prepared and know the main line, otherwise he will experience a torment over the board, trying to find the best moves over and over again. Coming back to Diemers improvement - Nc3, I said it has more psychological effect than scientific one, it is because if black can still play e5, then why it is an imrpovement? In practice after 3 Nc3 90 perc of all players wil answer with natural developing move Nf6 - protecting and developing a piece. What's wrong with that? Well, now that situation is completely different, because now after f3 black's e5 is just an error!. Yep, I told you that Nc3 is provoking black to react and to defend his pawn on e4. I even have a game played with a super GM in that line in blitz game.

So after Nc3 if black will not try to play end game with an early e5 and play something else, here where fun begins. Although I have to warn you that Blackmar-Diemer Gambit accepted is not like white is winning on the spot, no, there is no gambit in chess which is winning on the spot. There are at least 7-8 variations in which white can not even think about obtaining advantage, but the catch is that black must be willing to give up his pawn advantage. If you know your opponent is greedy, he is half beatened.

Summarizing my short history lesson about Blackmar-Diemer Gambit, after 

1d4 d5

2e4 dxe4

3Nc3 Nf6

4 f3 exf3

I have to say that the essence of that gambit is a half opened f-file. Because of that you will experience amazing possibilities over that file, including rook takes on f7 or knight on f6 leading to a deadly attack. Personally because of that gambit I could developped my potential of playing in tactical and combinational style, so if you are a gambiteer you will love that opening.

It is also a great way to cut-off your opponent's preparation on the move two. Just think about that, your opponent start to think on the move two. How ridiculous is that? or he may think that you are ridiculous by playing that. he will not be if he continues with a good looking moves.

At the end I would like to add that english is not my mother language, so if I will write cheese instead of chess, please don't make laugh on me. I will try to give you anything I know about my favorite opening for white. I hope my long time experience (almost 10 years) will add an extra wisdom to my analysis.

And finally have fun!