What is the technique for a cannon versus a lone elephant and a soldier?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws for movement, checkmate and both repetition rulings: a side that forces a repetition by perpetual check or perpetual chase loses rather than drawing. The chase half has not been validated against the official casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it before publishing.
Direct answer
Do not expect a forced win. The cannon has no screen of its own: your general can never serve as one, so apart from the two generals the only pieces the cannon can jump are the defender's elephant and soldier. Every check therefore depends on where the defender lets them stand. The soldier is also a threat in its own right, since it can generate its own counter-threats if left alone.
Why the screen decides everything
A lone cannon cannot even check a bare general, because there is nothing to jump. Here the elephant and the soldier are the only possible screens, and both belong to the defender, so the cannon side can only build a threat around a point the defender has chosen to occupy. A defender who keeps them off the general's file and rank leaves the cannon very little to work with.
What the cannon side can still try
Keep the soldier from becoming dangerous, and look for moments when the elephant has to stand on the general's file or rank, for instance on its one point inside the palace, at the front centre. If the soldier is lost, the elephant is the only screen left. The cannon side should keep probing, but it is looking for a defender's mistake rather than executing a known win.
Related questions
Is this an easier win than chariot versus elephant and soldier?
No, much harder. A chariot attacks on its own; the cannon needs a screen, and here every possible screen belongs to the defender.
Can the defender ever hold a draw here?
Yes. Keeping the elephant and soldier off the lines where they would serve as the cannon's screen leaves it few ways to give check at all.
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