[Event "?"] [Site "?"] [Round "0"] [White "Lucena"] [Black "?"] [FEN "4K3/2k1P3/8/8/8/8/3R4/5r2 w - - 0 1"] 1. Rc2+ {Diagram #} 1... Kb7 (1... Kd6 2. Kd8 {and the pawn will promote}) ( 1... Kb6 2. Rc4 Kb5 3. Rc8 Kb6 4. Rd8 Kc6 5. Rd7 {and the pawn will promote}) 2. Rc4 Rf2 {preventing White's king from cming to the f-file, but Black cannot keep the king tied behind its pawn any more.} 3. Kd7 Rd2+ { Black has nothing but checks or else White will promote} 4. Ke6 Re2+ 5. Kd6 Rd2+ (5... Kb6 6. Rc8) (5... Kb8 6. Rc5 Kb7 7. Re5) 6. Ke5 Re2+ 7. Re4 { Now Black cannot stop White's pawn from promoting. This technique is called building a} *