Ladder
A ladder is a sequence of moves in which both players play stones in straight lines, usually parallel to a nearby edge. Here is an example of a ladder:
In this example, Red is attacking and trying to make a connection to the bottom edge, whereas Blue is defending and blocking the connection at each step. If Red continues to play along the second row with the goal of connecting to the bottom, then Blue is forced to continue playing along the first row to prevent the connection.
Ladders usually occur close to an edge of the board, typically the edge belonging to the attacking player, whose stones are further from the edge than the defender's stones.
In the above ladder example, Red will eventually be able to force a connection to the bottom edge due to her ladder escape piece on the right of the second row:
Once the ladder reaches this ladder escape piece, Blue can no longer block the connection.
The ladder is named after how far the attacking player is from the edge. For example, the above diagram shows a second row ladder, also known as a height-2 ladder. A second row ladder is the most aggressive kind of ladder to defend against. Ladders can also form on other rows. Here is an example of a third row ladder:
In this case, Red will not succeed in connecting to the bottom because the red pieces on the right do not form a 3rd row ladder escape. If Red continues to push the ladder, Blue is able to successfully block it. For example:
Blue has successfully stopped the ladder from connecting.
Contents
Pre-ladder formations
It is useful to recognize some basic positions where a player can force a ladder to occur. These formations can appear at any distance from the edge. The examples below result in 3rd row ladders. If they are one hex closer to the edge, they give 2nd row ladders; if they are one hex further from the edge, they give 4th row ladders, etc. The first formation is called the bottleneck. In all cases, it is Red's turn.
Basic Terminology
Sometimes it is important to say exactly how close to the edge a ladder is. A second row ladder is a ladder where the attacking pieces are on the second row -- just one row from the attacker's edge. A third row ladder is a ladder where the ladder's attacking pieces are on the third row. One could in theory continue this pattern forever but in practice one rarely talks about sixth or higher row ladders. This is because even though these ladders do sometimes form, the general intention by the attacker is typically not to connect to the edge: the attacker may instead want to try to connect to another group of their own stones.
Another reason why ladders much higher than the fifth row are not often considered is that if a ladder is sufficiently high, the defender can just ignore it and play elsewhere, and the attacker may not be able to instantly connect. This means that for a sufficiently high ladder it seems impossible to formulate a notion of a ladder escape as the defender can ignore the ladder and play in the escape area without losing immediately.
What every player should know
Players should be able to recognise when ladders are forming, and be able to predict what will happen at the end of them without playing them out. Players should know the basic ladder escapes for second and third row ladders. Then players should learn how to create their own ladder escapes by understanding the basic ladder escape fork trick.
Ladder handling
There are three ways for the attacking player to "win" in a ladder situation:
- Making use of an existing ladder escape piece
- Creating a new ladder escape with a Ladder escape fork
- Cornering
