If we assume that {0}, it follows (through a Forcing X-Chain) that {1}. Therefore we can conclude that {2}.
Unary Chains start with a simple assumption that a cell is/not one of its potential values, which is proven to be either true or false.
X-Chaining means that:
(1) when a cell is assumed to be a value
then other possible positions for this value in this cells three region are
removed
(2) when a cell is assumed to not be one of its potential values
and there are only two positions for this value in one of this cells three
regions
then the other cell must be this value.
The forcing chain consists of a chain of implications based on simple rules. The chain is an X-Chain, because it only involves a single value. The details of the Forcing Chain are given below.
Note that Unary X Chains which contain 6 cells are also known as Turbot Fish.
Details of the Forcing Chain:
{3}