Why does the advisor only move diagonally in xiangqi?
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
It is a defining rule of the piece rather than something derived from anything else: the advisor moves one point diagonally, matching the two crossed lines drawn inside each palace. Because the palace is only three points wide, that single restriction is enough to limit the advisor to exactly five reachable points for the whole game.
What the diagonal lines are actually for
The X marked in each palace exists specifically to show the advisor's moves; no other piece uses it. The general, moving through the same box, ignores those lines entirely and uses only the orthogonal ones, which is a common early confusion for new players.
The consequence of being diagonal-only
An advisor in a corner can only ever go to the centre, and an advisor in the centre can go to any of the four corners, but never directly between two corners. That built-in slowness is part of why the advisor reaches so few points, despite being one of the most important pieces defensively.
Related questions
Could an advisor ever move orthogonally?
No, never; that is the general's movement, and the two pieces are deliberately built to be opposites within the same box.
Why is the advisor confined to the palace at all?
Because its entire purpose is guarding the general, which never leaves the palace either.
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