Tactics & checkmates
Fork
A fork is a double attack: one piece attacks at least two enemy targets at once. The opponent can often save only one, allowing a material gain. Knights are especially dangerous, but pawns, bishops, rooks and queens can also fork.
A practical example
A white knight moves from e6 to c7, attacking the black king on e8 and rook on a8. Black must answer the check first; White can then capture the rook.
A common mistake
Watching only the piece under attack. Before moving, check whether your king and queen or king and rook share a knight-fork square. Also check whether the forking piece can simply be captured.
Try this in your next review
Look for checks first, then attacks on undefended pieces. For every possible fork, calculate the strongest reply before counting the material you expect to win.
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