The Xiangqi Cannon Explained

The piece with no chess equivalent

Every other Xiangqi piece has some rough chess cousin. The chariot moves like a rook. The horse moves in the same L-shape as a knight. The cannon has no cousin at all. Nothing in chess needs a stranger standing in exactly the right spot before it's allowed to strike. Learn the cannon, and you've learned the one idea in xiangqi that chess never prepared you for.

One of Fun Xiangqi's tips puts it bluntly: "Your cannon has no screen yet — nothing to shoot over." That's the whole piece in one sentence. Let's unpack it properly.

If you'd rather meet the cannon alongside the rest of the army first, our rundown of every xiangqi piece is a good place to start.

How the cannon moves — and how it captures

Away from combat, a cannon behaves exactly like a chariot: any distance along a straight line, as far as the board and other pieces allow. Nothing tricky yet.

Capturing is where the cannon stops behaving like anything else on the board. It can only capture by jumping over exactly one piece — either colour — somewhere along the line it's attacking, then landing on the first enemy piece past it. That piece in the middle is called the screen (in Vietnamese, "ngòi"). No screen, no capture. Two pieces in the way, also no capture. Exactly one, and the cannon fires clean over the top.

This single rule is why a cannon feels less like a rook and more like artillery lobbing a shell over a wall.

The screen: the trick that makes cannons work

Picture a cannon looking down an open file at an enemy piece with nothing at all between them. It's tempting to assume the cannon can just take it — but a cannon capturing without a screen simply isn't legal. Let's check three situations on the same file, with the cannon at the bottom looking up the board.

Legal capture — exactly one piece in between:

rank 6:  X   <- black chariot, the target
rank 5:  .
rank 4:  .
rank 3:  S   <- a soldier, the screen (only piece between cannon and target)
rank 2:  .
rank 1:  C   <- red cannon

One piece, S, sits between the cannon and the chariot. Empty points don't matter — only the count of occupied ones does, and here that count is one. The cannon jumps clean over S and captures the chariot.

Blocked capture — two pieces in the way:

rank 6:  X   <- black chariot, the target
rank 5:  .
rank 4:  S2  <- a second piece
rank 3:  S1  <- a first piece
rank 2:  .
rank 1:  C   <- red cannon

Now two occupied points sit in between: S1 and S2. A cannon needs exactly one screen, so two pieces stacked in the way makes the capture illegal — no matter how far the cannon could otherwise reach.

No screen — a wide-open line:

rank 6:  X   <- black chariot
rank 5:  .
rank 4:  .
rank 3:  .
rank 2:  .
rank 1:  C   <- red cannon

Every point between them is empty. Nothing to jump over, so no capture — even though a chariot standing here would win the piece instantly. The cannon can still slide up that file as an ordinary, non-capturing move, but it can't land on the chariot's point without a screen sitting somewhere in between.

Three positions, one rule: zero screens or two-plus screens means no capture; exactly one means fire away.

Building and breaking a screen

Because a screen can belong to either side, both players are constantly changing the number of pieces sitting between a cannon and its target — sometimes on purpose, sometimes as a side effect of a completely different plan.

Add a piece into an empty gap, and a cannon that couldn't threaten anything suddenly can — one screen where there used to be zero. Add a second piece into a gap that already had one, and the opposite happens: a live threat gets shut off, since two screens is just as illegal as none.

The reverse works too. Pull a piece out of a gap that had two screens, and if nothing takes its place, the count drops to one — and a cannon that looked harmless a moment ago is suddenly attacking. This is the cannon's signature trick, the discovered check: a piece moves away for some unrelated reason — to capture something, to escape danger, to defend elsewhere — and the general finds itself staring down a cannon that wasn't a threat one move earlier. Because the piece that moved doesn't look like it delivered the check itself, these are easy to miss until they land.

Cannon partnerships

Cannons rarely work alone for long. Two partnerships show up constantly once you start playing real games.

Horse and cannon. A horse moves in an L-shape to control points right next to the enemy general — points the general can't step onto without walking into check. (New to that move? Our look at the horse versus the chess knight covers it in detail.) A cannon, once it has a screen in place, attacks along a straight file or rank from much further away. Because the two pieces threaten the same area from completely different angles — one stepping, one shooting — a defender who blocks the cannon's line often finds the horse still covering the escape point, and the other way around. That's why horse-and-cannon attacks are a middlegame staple.

Double cannons. Two cannons on the same file or rank get dangerous in an unusual way: the piece a defender places to block one cannon's line can become exactly the screen the other cannon needs. Blocking one attacker can hand the second its shot.

Value shifts, and the cannon's signature opening

A cannon's value depends heavily on how many pieces are still on the board. Sources differ slightly on exact numbers, but a common rough guide — chariot around 9 — rates the cannon at about 4.5, close to a horse's 4, an advisor or elephant's 2, and a soldier's 1 (roughly 2 after crossing the river). What that single number misses is timing. Early and mid-game, with plenty of pieces around to serve as screens, a cannon usually rates a touch above a horse — there's almost always a shoulder to fire over. Deep in the endgame, with fewer pieces left, screens run scarce and cannons lose their bite, while a horse — never needing a screen at all — tends to age better.

That early-game strength is exactly why the most common way to open a game of xiangqi puts a cannon front and centre. The Central Cannon opening (中炮, "pháo đầu" in Vietnamese) moves a cannon straight to the middle file, aiming down the board at the opponent's own centre before either side has developed much else. It's aggressive, easy to understand, and usually the first opening a beginner ever meets. For a full walk-through of how openings work and what a solid reply looks like, our guide to beginner openings and strategy walks through it.

Quick questions

Can a cannon capture without a screen? No. Zero pieces in between means no capture, even along a completely open line — the cannon simply can't take that piece yet.

Can the screen be my own piece? Yes. The screen can belong to either side. That's exactly why moving your own pieces around can create or shut down a cannon threat without you meaning to.

Why does the cannon lose value in the endgame? Fewer pieces means fewer possible screens, so a cannon runs dry more often. A horse, needing no screen at all, tends to matter more once material thins out.

Is the screen the same as a pin in chess? Not really. A pin stops a piece from moving. A screen is what a cannon needs to capture at all — change the count and you change whether the cannon can fire, not whether some other piece is free to move.

Fun Xiangqi's challenge chapters start with cannon basics, so you can drill the screen rule against real puzzles instead of just reading about it. Give it a try and see how fast it clicks.