Black has definitely more attacking chances with d5 (as played later), so white better prepares to defend. First thing, bring protection to d3. It is not attacked now, but it will be when black opens the d column. Na3, for a quick castling (welcoming BxN, despite the doubled a pawn), seems necessary. Because (among other things), from f2 (the next step) white will control e3. And the Bdsb would like very much to go there, now that the Ne2 makes it free from the king's attack.

It is a good idea because white is still underdeveloped, and it is not so easy for him to brings defenders to the d column. Black "threats" dxe, uncovering the d column.

In my view, and in view of the danger represented by the opening of the d column, this was not the worst choice at all. This way, white "wins" the chance to get Ne2 to f5, and this is very good. White can easily add defenders to e4 (a white square), and that will control black's phalanx.

White here accepts a possible BxN, the very weak doubled pawn on a rim. In return, he will have got free from the nasty dominance of this powerful B. So white can trust black wouldn't exchange. But, as Nb5 is not a real threat, I think white wants to put the N on c2, pressing on d4. I prefer Nd2, too, though.

Having opened (and I hope, sooner or later, white will exploit it...) the g column, it was a good bet saying that B would have castled - if ever - queenside, where white seems to have no attack at all. But this has its downsides: f6 is now weak for black, and white, as well stated before, will try to open this column exchanging (safely) the f pawn with the black's e one. Not easy, though. I would have played Ke7, maybe. On the other side, white does have some disturbing moves like b4, b5... trying to distract black from building a central attack.

This move only helps black to put the B on e3...

...and now, Nc2, as predicted. Black would have to accept to retire the B or go for d4!?, fxe4, exd4, which looks a sure white death at first sight (maybe some reader can work on it...).

Opening the e column, first thing. Well done.

The bishop shouldn't be moved from this previleged position unless unavoidable. If you take with the N and white exchanges, the B will end on d5, threatening the Ra1, which would have a tempo to play Rd1 - a good move - causing the B to lose a tempo to retire. Better, in any case, than the text.

As you see, Jkarp...

Black was trusting on d5 to defend the N, that otherwise, from here, can only go to a4. Retiring to d4 was just make a present to white: Rd1, and the N must move again.

I agree with isaiah11. This pawn was defended, the fight is for the central columns.