We have been through 3 of the 4 main responds from white after 1. e4 e6 2. d4 d5. Only 1 to go now...
3. Nc3 is the most popular respond in the master level of French defense, and it has a reason for that.
3. Nc3 is not as aggressive as the Tarrasch variation, but still is very complicated line to play for both white and black. Against 3. Nc3 variation I recommend the "Winawer variation" as the main respond. The classical variation(....3. Nf6) is also very playable, but its more passive and you can have some dark square weaknesses.
We are going to look at the Winawer variation firstly. The Winawer variation starts after you play ....3. Bb4 against the 3. Nc3 variation. And its main idea is to develop your dark square bishop and then to play c5. So that your dark square bishop will not be stuck behind the pawn wall.
Normally white will play e5 in the position above(since the e4 pawn is hanging because the c3 knight is pinned) and then try to kick your dark square bishop out with the move a3. And you should continue with your plan which is the c5 pawn break.
The main line goes 5. a3 Bxc3, 6. bxc3 Qc7, 7. Qg4 Ne7 8. Qxg7 Rg7 9. Qxh7 cxd4
This is a very spicy line and have a lot of theory. It makes the board very complicated and black often times gets a huge development lead and have a lot of open lines to attack. But you sacrificed a pawn and now white can just push his pass h pawn and make a queen. So you need to be careful.
Let's go some steps back. After you played the move ....3. Bb4, white doesn't have to play e5. But if they play something like Bd3, Nd2 and so on. You can just play your original French defense idea with the c5 pawn break. And often times white will play e5 and Qg4 anyway. So there you go, now you have a weapon against 3. Nc3 variation.
As you can see above. White lost his pawn and now have some problem to deal with. So the move order can cause some huge trouble for white.
We are also going to be looking at the classical variation(....3. Nf6). I actually play this line before i learned the Winawer variation. It is basically the same as Tarrasch variation with ....3. Nf6. And your plan is just to play the original French defense idea c5 pawn break.
You might get some position as above. but you should just continue with your original idea.
Quick review: Against 3. Nc3 variation just play the spicy Winawer variation which has a lot of theory(which I of course studied), or the more solid and classic Classical variation(....3. Nf6) with the original c5 pawn break idea.
Hope you enjoy if you read so far. I know this blog is kind of short but I think I covered most of the ideas. Comment below if I forgot anything or if you want to. Have a nice day!