Which xiangqi pieces can never deliver checkmate by themselves, no matter how many you had?
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
The advisor and the elephant, no matter how many you have. Checkmate requires directly attacking the enemy general, and both of these pieces are permanently confined to their own half of the board, the advisor inside its own palace and the elephant behind the river. A hundred advisors could not deliver check on their own, because not one of them could ever reach a square near the enemy general.
Why quantity does not fix it
With every other piece type, more copies eventually mean more attacking power somewhere on the board. Advisors and elephants are the exception: their movement rules are a hard boundary, not a matter of degree, so no amount of material of just those two types changes what they can reach.
What they contribute instead
Their value is entirely defensive and entirely indirect: they can support a mate by removing the general's own escape squares, or by shielding an attacking piece, but the final blow always has to come from a chariot, cannon, horse, soldier, or the general itself under the flying-general rule.
Related questions
Can an advisor or elephant assist in a mate even though it can't deliver one?
Yes, very often, by occupying a palace point the general would otherwise use to escape.
Is the general in the same category?
No, unlike the advisor and elephant, the general can occasionally deliver check itself, through the flying-general rule.
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