approach liberty
The approach liberties of a group is the minimal number of the attacker's excess approach plays necessary for removal. [1]
The white semeai string hast 2 while the black semeai string hast 3 approach liberties.
Timm(10k): Hi Robert. I do not understand this page. According to the definition given, I feel like black has one approach liberty and white doesn't have any. Thus the black group would have two primary and one approach liberties. Am I wrong ?
[1] The definition follows that one in the book Capturing Races 1.