Now 16...Nfe4 would run into 17.Ne5.

Consistent strategy: White still intends to play Ne5 followed by f2 -f3 and e2-e4, but again does not want to allow an exchange of one minor piece.

Black has managed to exchange one pair of knights, but in the meantime White has regrouped and played f2 -f3 , which results in the immediate threat of e2-e4. Black now went wrong with . . .

. . . and Nielsen had no trouble converting his advantage.

Again we see two knights defending each other, tempting White to go for the ambitious and audacious . . .

Keeping all the minor pieces on the board. If White succeeds in driving the black pieces back from e4, his opponent will struggle with his pieces in a passive position.

Trying to immediately rid himself of his superfluous knight by force.

The unusually-placed rook on b4 still makes it difficult for Black to coordinate his pieces.