Soon Hellers sacked, or lost, an additional Exchange. In any case, the attack seemed to be breaking through. But the unflappable Ivanov threw back the extra rook in order to get the queens off the board. Suddenly, Hellers was up a pawn. But his pieces were woefully unprepared for the pawn race which ensued.
Hellers chooses the only line which maintains the initiative.
By leaving the e6 pawn on the board, Black preserves the option of playing Rh8-g8. Qc6, exploiting White's overloaded pieces. Black has activated the dark-squared bishop but still has problems with his knights. Rg8 which stops White's plan g4-g5. White cannot allow Black to post the bishop at e5, so he must play 21 f5.