Tactics & checkmates
Double attack
A double attack creates two threats at once. They may target pieces, combine a mating threat with a material gain, or attack two different tactical weaknesses. A fork is a common double attack by one piece; coordinated pieces can also create two threats.
A practical example
A queen gives check while attacking an undefended bishop. If the opponent must move the king, the queen can capture the bishop next. The key question is whether a single defence can answer both threats.
A common mistake
Confusing two threats with a guaranteed gain. A countercheck, exchange or move that protects both targets may refute the idea.
Try this in your next review
After choosing a candidate move, state its two threats. Then deliberately search for an opposing reply that neutralizes both. Count the gain only after that defensive check.