Why does tempo matter so much when attacking the general?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws and is regression-tested against the official 110-diagram repetition casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it against the engine before publishing.
Direct answer
Because the general is trapped inside nine fixed points, an attacker who keeps generating threats never lets the defender spend a move on anything but responding. Since most defences are saved by getting an extra defender into the palace in time, every tempo the attacker forces is a tempo the defence doesn't get to use for reinforcement.
The race that decides most attacks
A xiangqi attack on the palace is usually a race between how fast the attacker can bring enough force to bear and how fast the defender can bring a spare advisor, elephant, or piece back to help. A single wasted, non-forcing move by the attacker can be exactly the tempo the defence needed to survive.
Why quiet defensive moves are so costly for the defender too
The same logic cuts both ways: a defender who spends a move on something other than the most urgent need is effectively giving the attacker a free tempo as well, which is why calm, accurate defence under pressure is one of the harder skills in the game.
Related questions
Does this mean every attacking move should be a check?
Not necessarily, but every move should either be forcing or clearly necessary; purely optional moves during an attack are usually a mistake.
Is tempo less important in quiet, non-attacking positions?
Somewhat, yes, positional manoeuvring gives both sides more room to make non-forcing moves without immediate consequence.
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