Set play in chess problems

Set play

Definition

In chess composition, set play is the play that already exists in the diagrammed position before White’s key move. In other words, if the side to move were hypothetically reversed (Black to move first in a White-to-play problem), the prepared mating replies that White would deliver to Black’s different defenses are called the set play. A “set-mate” is a mate that is already prepared in the diagram for a particular Black move, even before the key is made.

Set play is contrasted with the variations that occur after the correct key (post-key play) as well as with near-keys or tries that almost work but fail to a specific defense.

• Set play = prepared responses from the initial diagram (often “Black-to-move” lines in a White-to-play problem).
• Key = the problem’s intended first move by the composer.
• Post-key play = the variations that occur after the key is made.
• Set-mate = a specific mating reply that is already “set.”

Compare with: Post-key play, Try, Threat, Virtual play, Sound, Dual.

How set play is used in chess problems

Usage

Set play appears most commonly in directmates (e.g., mate in 2 or 3), but it is also relevant in helpmates, selfmates, and other genres. Composers deliberately craft positions with rich set play so solvers can appreciate how the key move preserves, refines, or changes those pre-existing mates. Good set play often foreshadows the thematic content of the problem: changed mates, changed defenses, cycles, thematic dual-avoidance, and more.

• In a twomover, the diagram is White to move, mate in 2. The set play lists how White would already be ready to mate “if Black moved first.” Then, after the key, the composer shows how the mates are preserved or intentionally changed.
• Editors typically annotate problems with lines like “Set: 0...a? 1. X#, 0...b? 1. Y#; Key: 1. K! (threat ...), 1...a 2. Y#, 1...b 2. X#,” highlighting changed play.

While set play is fundamental in composition, the term is rarely used in practical OTB chess; over-the-board players would instead say “if Black moves first, then...” without using the compositor’s terminology.

Strategic and historical significance

Why it matters

Set play is one of the most important lenses through which problemists evaluate the artistry of a work. It allows the composer to set up “pre-echoes” (anticipated mates) that may later be altered, transposed, or cycled after the key. The tension between set play and post-key play is the heart of numerous themes:

• Changed play and cycles, e.g., Lacny cycles and Zagoruiko transformations.
• Interference and block themes (e.g., Grimshaw, Novotny ideas) where set mates switch squares or pieces after the key.
• Economy and purity: clean set mates without unwanted Duals are prized; unintended set mates can become Cooks.

Historically, 19th- and early 20th-century masters like Sam Loyd, Comins Mansfield, Lev Loshinsky, and others developed problems where elegant set play is transformed by a quiet key. Schools such as the Bohemian tradition emphasized model mates and harmonious set lines that “change” beautifully after the key.

Examples and motifs with set play

Example 1: A schematic twomover with changed mates

This is a typical “textbook” structure illustrating what composers mean by set play and changed play (no full diagram is necessary to grasp the idea):

• Set play (Black to move from the diagram):
  • 0...a? 1. Qa4#
  • 0...b? 1. Qe4#
  • 0...c? 1. Qg4#
• Key: 1. Qh5! (White to move; quiet key, creating a new threat, say 2. Qe2#)
• Post-key play (after 1. Qh5!):
  • 1...a 2. Qe2# (the mate to 0...a? has “changed”)
  • 1...b 2. Qg2# (again, changed)
  • 1...c 2. Qa2# (changed a third time)

Even without a specific diagram, this schematic shows how set play (Qa4#, Qe4#, Qg4#) can be reversed or cycled into different mates after the key. That switch is the essence of changed play and is a hallmark of many award-winning twomovers.

Example 2: Set play in helpmates

In a helpmate in 2 (stipulation: h#2), set play often lists the intended cooperative moves if Black were to move first from the diagram, e.g., 0...a 1. b c 2. d#; after the key, the exact order of cooperation changes, or a new interference is introduced that forces the mates to occur in another sequence. The “set solution” is what would happen before any preparatory key by White in the published diagram.

How editors annotate set play

In problem magazines, you’ll commonly see compact notation:

• “Set: 0...a? 1. X#, 0...b? 1. Y#. Key: 1. K! (threat 2. Z#). 1...a 2. Y#, 1...b 2. X#.”
• Tries are noted separately: “Try: 1. T? (threat), but 1...d!” showing why the near-solution fails.

Related terms: Try, Threat, Post-key play, Virtual play, Cook, Sound, Model mate, Echo.

Interesting facts and anecdotes

Trivia

• Set play is a litmus test for a problem’s clarity: unintended set-mates can create accidental solutions (cooks), forcing the composer to refine the position.
• Many prize problems win because of the elegance of their set play versus post-key play contrast—a signature of the Bohemian style.
• Composers sometimes design a problem specifically to show that every set-mate changes after the key (a full change), or that the mates cycle among defenses (e.g., Lacny or Zagoruiko cycles).

Practical tips for solvers and composers

For solvers

• Before hunting for the key, list the set play: ask “If Black moved first here, what mates are already prepared?”
• Use set play to detect themes—are there neat mates to different Black moves that might be intentionally rearranged after the key?
• Watch out for Duals in set play; elegant problems often avoid multiple possible mates to the same defense.

For composers

• Draft the set play early, then search for a quiet key that preserves the logic while changing mates or defenses in a thematic way.
• Check for unwanted set duals and accidental solutions (Cooks), and aim for Sound construction.
• Consider showcasing a named theme—e.g., a Grimshaw or Novotny—expressed in both set and post-key play for maximum effect.

Frequently asked questions about set play

Is set play the same as the threat?

No. The threat is what White intends to do after the key move if Black does nothing effective (e.g., “Key: 1. K! threatening 2. Mate”). Set play, by contrast, describes mates that were already prepared in the initial diagram (if Black moved first), before any key.

Can a problem have no set play?

Yes. Some excellent problems have minimal or no interesting set play; their beauty lies entirely in the post-key variations or deeper ideas like paradoxes and sacrificial keys. But when set play is rich, it often enhances the solver’s experience.

Does set play exist in real games?

The concept is composition-specific. OTB players don’t typically label anything “set play,” though they sometimes analyze “if the opponent moved first...” scenarios during calculation. The formal term belongs to problem chess and is used by a Problemist.