Why Did White Lose in Reshevsky - Smyslov 1945?

The next game in Smyslov's Sparklers is the second game of the Smyslov - Reshevsky mini-match on board no.2 of the 1945 USA-USSR radio match. Smyslov won the first game with White and it's a safe assumption that Reshevsky was looking to even the score.

I've played through the game several times. It's a complicated Slav Defense, a real example of chess at the highest level. It's at such a high level that I have a big problem with it -- I don't understand why Smyslov won. My first suspicion was that Reshevsky lost in the opening. Since I don't play 1.d4 very often, and have never been a big fan of the Slav as Black, my knowledge is severely limited.

In the diagrammed position (after 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 dxc4) he played 5.e3, the least popular of the three most common moves in the position. Using Chesslab.com, I found 97 games played since 2002 (Chesslab had a system crash a few years ago and lost many games from 2002) with at least one player rated over 2700. Of these, 94 continued 5.a4, two continued 5.e4, but there were no examples of 5.e3. Is there an obvious problem with it?

Radio Match 1945
Smyslov, Vasily

Reshevsky, Samuel
(After 4...d5xc4(xP))
[FEN "rnbqkb1r/pp2pppp/2p2n2/8/2pP4/2N2N2/PP2PPPP/R1BQKB1R w KQkq - 0 5"]

Looking at 5.e3, I found 65 games with at least one player rated over 2400 (played since 1997, when the Chesslab database starts keeping track of ratings). Most of these continued 5...b5 6.a4 b4 as in the reference game. About two-thirds of these continued with Reshevsky's 7.Na2 rather than the main alternative 7.Nb1. Now after 7...e6 8.Bxc4, I found three moves played with about equal frequency: 8...Nbd7, 8...Bb7, and 8...Be7. I suspect that these moves are largely interchangeable and a few searches convinced me that this is probably true. Kasparov thinks 8...Bb7 is more accurate, but that's not the issue here.

Smyslov played 8...Be7, and the game continued 9.O-O O-O 10.Qe2 Bb7. Here I found a total of 23 games that reached this position (by players at all levels). A quick look through the games convinced me that White has a satisfactory position, maybe even a slight advantage.

If Reshevsky didn't lose the game in the opening, where did he go wrong? I'll continue the analysis on another post. To play through the complete game see...

Samuel Reshevsky vs Vasily Smyslov, 02, USA-URS radio-m 1945
http://www.chessgames.com/perl/chessgame?gid=1125477

...on Chessgames.com.