The Cozio defense arises after these moves:

```
[FEN ""]

1.e4 e5 2.Nf3 Nc6 3.Bb5 Nge7

```

At first, this looks like just another dubious opening, but I found it surprisingly hard to prove an advantage with white. 

```
[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Bb5 Nge7 4. O-O g6 5. c3 Bg7 6. d4 exd4 7. cxd4 d5 8. exd5 Nxd5 9. Re1+ Be6 10. Bg5 Qd6 11. Nbd2 O-O

```

It is not clear how white should proceed. There are many options, but black has several different ideas and can quite easily general counter-play. Going 12. Ne4 Qb4 13.Bxc6 bxc6 seems like the most principled approach, but black is just fine in these lines. He can drum up quite interesting play judging from the grandmaster games I looked at. This line:

```
[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Bb5 Nge7 4. Nc3 g6 5. d4 exd4 6. Nd5 Bg7 7. Bg5 h6 8. Bf6 Bxf6 9. Nxf6+ Kf8 10. O-O 

```

is given by some FIDE-Master on YouTube, but I'm also not very convinced. I just fail to see white's advantage in this position. So, I have two questions:

* Why is the Cozio defense played so rarely?
* What is, in your opinion, the best way to secure an advantage against it as white?