The Rook is twice assailed and twice defended, hence on White's Q4 the forces are even; in spite of this the Rook is lost, because the defending Queen is assailed. White plays QxQch. Now the Rook cannot save itself either by R-Q8ch., or by R-X5ch., because Black is in Check. Black replies XxQ. After this interlude, White has gained the superiority on Q4 and captures the Rook gratis.