Simple endgame lessons from the US championship

      After nine rounds of the 11-round US championship, grandmaster Wesley So leads with 8 points. GMs Jeffery Xiong and Ray Robson are tied with 7.
In round 9 on Wednesday, So and Robson — seconds apart — simplified to pure pawn endings (the easiest type of ending to win) by sacrificing rooks for bishops when they knew their kings would occupy a critical square afterward.
      In any endgame of king plus pawn vs. king, the strong side should suss at a glance if it’s a win by either 1) queening the pawn because the enemy king is “outside the square of the pawn“, or 2) occupying one of the pawn’s “critical squares” with the king.

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