Why is a chariot check considered easier to calculate than a horse check?
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 a chariot's threat has exactly one condition, and it is easy to see. A chariot checks along a straight line with nothing between it and the general; you can trace that line with your eye and know immediately whether the check exists. A horse's check depends on its leg being open, a separate point that has to be checked independently, and one that can quietly change status after almost any move elsewhere on the board.
What makes the chariot's case simple
There is nothing hidden about a chariot's line of attack. If the path to the general is clear, the check is real; if anything at all sits on that path, it is not. One glance settles the question, and it stays settled until something actually moves onto or off of that exact line.
What makes the horse's case harder
A horse threatening the general depends on a leg point that is physically nowhere near either the horse or the general, so it is easy to check the wrong thing and miss it. A piece moving for a completely different reason, several squares away from both the horse and the king, can silently open the horse's leg and create a check that was not there the move before.
Related questions
Does this mean horse checks are more dangerous?
Not more dangerous exactly, but more often missed in calculation, which has much the same practical effect over the board.
Is a cannon check similarly tricky?
Yes, for a related reason, its screen has to be checked as a separate condition from the line itself, just like a horse's leg.
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