How do you write a move when two pieces are on the same file?
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
You replace the file number with a position word. Chinese uses 前 (front) and 後 (rear); WXF uses + and −. So 前炮平五 and +C=5 both mean "the front of the two cannons on this file traverses to file five".
Which one is the front
The one nearer the opponent, from the moving side's point of view. So Red's front cannon is the one further up the board and Black's front cannon is the one further down — the same physical piece is "front" for one side and would be "rear" for the other.
Three or more on a file
Rare but it happens with soldiers. Chinese then uses 前, 中, 後 for three, and for more than three uses positional numbers counted from the front. In WXF the same idea is written with a number before the piece letter.
Related questions
Does this apply to any piece type?
Any two identical pieces on the same file — cannons, chariots, horses or soldiers.
What if the two pieces are on different files?
Then the ordinary file number identifies them and no prefix is needed.
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