Count the liberties
When two groups that cannot both live share liberties, they fight a capturing race: each fills the other's liberties in turn, and the side that reaches zero last wins. Reading one is counting, not fighting — outside liberties for each side, then shared liberties, then the move order, since the player to move effectively gains one. Eyes are the great multiplier: a group with an eye cannot be filled from inside, so an eye-versus-no-eye race is a rout. When the counts are close, hunt for the tesuji — a throw-in or a snapback (6.4) that steals a liberty at the source. Here the count is blunt: White's column has one liberty, Black's chain has four. Black to play: finish it.