@Jayboman1579
The move 3. … e5 in the above position is called a pawn lever. It is a thematic move to attack the base of the opponent's pawn chain (attack the base, weaken the whole chain) and favorably open lines for your pieces. For experienced players, the move 3. c5 would seem a little dubious and immediately spur thoughts about playing 3. … e5 in response.
You can google the term, and there are a variety of really good internet resources that can explain and expand the topic for you.
@Paul-Leggett
Thanks! I hadn't heard of the term "pawn lever" before. I'll definitely look more into that.
My favorite place for research into openings is actually Wikipedia. I'll download the contents of an article in a PDF and reread it as needed. I haven't checked out the Slav yet, which I think it shows, I'll have to check out next.
@KnightStalker47
Thanks for taking the time to post that. I'll print that out for next time, just in case. I've actually seen more open a (or h) files lately. I've been looking for opportunities to practice a "rook lift" of some sort.
Thanks for the help, everybody!
I tried to post this a few days ago but unfortunately it got rejected because it contained several links (useful ones!). I've modified it to remove the links, I hope it still makes sense.
The internet was made for chess, both for playing and for studying. One of my favourite sites for the latter is 365chess. It lets you quickly explore opening moves to see what replies are most popular and how successful they are. You need to visit the site and click on "Opening Explorer" - you may need to create a (free) account.
In this case, after 1. d4 d5 2. c4 c6 we see that 3. c5 is White's 8th most popular move and that Black scores a whopping 60.6% in games where White plays this move!
Clicking on 3. c5 shows you the replies that Black has tried.
The most popular reply and the one favoured by whatever engine is used by 365chess is 3. ... Nf6. However 3. ... e5 is very successful - out of the sixteen games in the database, White won two, Black won fourteen and none were drawn!
The way I use the site is to play through as many games by strongish players that I can be bothered with to make sure that the sort of positions which crop up suit my style.
@jayboman1579 saidThe white push 3.c5 in a d4-pawn game is a theoretical error, as the high win ratio for black indicates. This is much too early for such an advance, as it releases the tension, does not hamper black's further development, leaves the d4-pawn potentially backward, and does not gain any significant territory in the black camp. Unlike the apparently similar advances for white (e5) in the Caro-Kann and French Defense, which do cramp black's development and gain significant ground.
What the correct idea for black after 1d4 d5 2.c4 c3 3.c5 ?
I'm not playing it right now, but have an irrational (probably) fear of it. What should I do next?
Caro-Kann Advance variation:
Analogously in the French:
@moonbus
I appreciate the time you took to post that. Nice theory approach. The things I keep learning!