What the !

Every so often I look at a game where the annotator awards an exclamation for a quiet retreating move that neither starts or continues an attack nor defends a position in some clever way. This often happens in Chess Informant. When I have the time I try and make an effort to understand why the annotator awarded the praise and most of the time I don't get it. Luckily some of the games are also available in other games collections. Here is a case in point: