Babson Task

 A Babson task is a direct-mate chess problem with the following properties:

   1.  White has only one key, or first move, that forces checkmate in the stipulated number of moves.

   2.   Black's defenses include the promotion of a certain pawn to a queen, rook, bishop, or knight. (Black may have other defenses as well.)

   3.  If Black promotes, then White must promote a pawn to the same piece to which Black promoted in order to complete the solution.

Babson Task Wikipedia Page

Combining 4 promotions from black with 4 echo promotions from white was the Holy Grail of chess for over a century. The greatest composers failed to compose this task. Then there was a 26 year old soccer trainer from Russia, who realized the impossible: Leonid Yarosh (source: De man die de Babson Task wilde maken - Tim Krabbé)

Articles Revisiting Tim Krabbé and Babson - Chessbase Article The perfect Babson - Chessbase Article

Babson Task - Very Nice Academic Kids Article Explaining the different types of Babson problems and History. LiChess Study THE BABSON TASK - 6 Chapter Study w/ Leonid Yarosh Composition and Bachmann Composition Videos The impossible Babson Task - 17 Min Video A Chess Composition Masterpiece ♚ The Babson Task ♚ Leonid Yarosh, 1983 - 12 Min The Most MARVELOUS Position to Ever Grace the Chess Board - 14 Min