Difference between revisions of "Ladder escape fork"

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A [[Multiple threat|forking move]] which creates a [[ladder escape]].
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A ladder escape fork is a move that creates a [[ladder escape]] while also threatening another connection. It is a kind of [[double threat]].
 +
 
 
== Example ==
 
== Example ==
  
Line 47: Line 48:
 
       Ha7 Hb7 H2c7
 
       Ha7 Hb7 H2c7
 
</hex>
 
</hex>
 
== How far can the attacker climb? ==
 
 
The effectiveness of a potential fork can be measured by how far the attacker can potentially [[climbing|climb]]. Let us consider some typical ladders and potential forks:
 
 
=== 2nd row ladder ===
 
 
In the first example, Red's space is limited. Red can climb to the 4th row, potentially [[bridge|bridging]] to a stone on the 6th row.
 
<hexboard size="6x7"
 
  coords="hide"
 
  contents="R a5 b5 c5 B a6 b6 c6 d4 f5 R 1:e5 B 2:d5 R 3:f3"
 
  />
 
 
If Red has slightly more space, Red can climb to the 5th row, potentially bridging to a stone on the 7th row.
 
<hexboard size="6x7"
 
  coords="hide"
 
  contents="R a5 b5 c5 B a6 b6 c6 f5 R 1:e5 B 2:d5 R 3:e4 B 4:d4 R 5:f2"
 
  />
 
 
Finally, in a [[switchback]] situation, where a 2nd-to-4th row switchback would allow Red to connect, Red can climb to the 6th row, potentially bridging to a stone on the 8th row.  This kind of forking ladder escape is called a ''switchback fork''.
 
<hexboard size="6x7"
 
  coords="hide"
 
  contents="R a5 b5 c5 a4 B a6 b6 c6 f5 R 1:e5 B 2:d5 R 3:f3 B 4:e3 R 5:g1"
 
  />
 
 
Of course, there are many variations of this, depending on what other pieces Red and Blue have on the board. But the three basic patterns shown above are the most common, and are good starting points for planning more complex ladder escape forks.
 
 
=== 3nd row ladder ===
 
 
The situation for 3rd row ladders is largely similar to that of 2nd row ladders. In the most constrained case, Red can climb to the 5th row, potentially bridging to a stone on the 7th row.
 
<hexboard size="7x7"
 
  coords="hide"
 
  contents="R a5 b5 c5 B a6 b6 c6 d4 g5 R 1:e5 B 2:d5 R 3:f3"
 
  />
 
 
If Red has slightly more space, Red can climb to the 6th row, potentially bridging to a stone on the 8th row.
 
<hexboard size="7x7"
 
  coords="hide"
 
  contents="R a5 b5 c5 B a6 b6 c6 g5 R 1:e5 B 2:d5 R 3:e4 B 4:d4 R 5:f2"
 
  />
 
 
Finally, in a [[switchback]] situation, where a 3nd-to-5th row switchback would allow Red to connect, Red can play a switchback fork and climb to the 7th row, potentially bridging to a stone on the 9th row. This is extremely threatening; note that on an 11×11 board, the 9th row is almost on the opposite side of he board.
 
<hexboard size="7x7"
 
  coords="hide"
 
  contents="R a5 b5 c5 a4 B a6 b6 c6 g5 R 1:e5 B 2:d5 R 3:f3 B 4:e3 R 5:g1"
 
  />
 
 
=== 4th row and higher ladders ===
 
 
The situation for 4th row and higher ladders is essentially similar, provided that the attacker can guarantee that the pivot piece connects to the edge. For example, in the following situation, the pivot piece "1" is not connected to the edge, and Blue could [[foiling|foil]] by playing at "a":
 
<hexboard size="6x9"
 
  coords="hide"
 
  contents="R d3 e3 B c4 d4 e4 b2 i2 R 1:g3 E a:g4 E *:c3 *:i5"
 
  />
 
However, if Red had, for example, one more piece at either of the locations marked "*" (or pretty much anywhere else near the bottom edge), then the pivot piece would be sufficiently connected for the fork to work in the same way as for 2nd or 3rd row ladders.
 
  
 
== See also ==
 
== See also ==
  
[[Foiling ladder escapes]]
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* [[Foiling]]
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* [[Climbing#Climbing from a ladder|Climbing from a ladder]]
  
 
[[category:ladder]]
 
[[category:ladder]]
 
[[category:intermediate Strategy]]
 
[[category:intermediate Strategy]]

Latest revision as of 01:53, 18 May 2022

A ladder escape fork is a move that creates a ladder escape while also threatening another connection. It is a kind of double threat.

Example

In the following position, Red has no edge template.

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The only option seems to be a ladder.

abcdefg12345671324

However, pushing the ladder too much is useless, and it actually enables Blue to win.

abcdefg1234567135246

Red needs the two pieces at the top right hand-corner of the board. Red pushes the ladder just enough to use a ladder escape fork. Piece number 3 is called the pivot piece. It threatens to connect to the top group and acts as a ladder escape as well.

abcdefg1234567132

See also