Eunuch Chasing the Emperor: Xiangqi's Soldier Checkmate

Why one Soldier is enough

A Soldier that has crossed the river attacks the point in front of it and the points on either side. So when it gives check, it is standing right next to the General. A check from an adjacent piece cannot be blocked, which leaves the defender two answers: capture the Soldier or move the General.

Your job is to take both answers away. The Soldier needs a guard, so the General cannot take it, and the General's sideways steps need to be covered, so it has to retreat. When each check leaves exactly one legal move, the Soldier can simply walk forward and ask the same question again, until the General reaches its back rank and runs out of points.

The helper that does this best is often your own General. Under the flying General rule, the two Generals may never face each other on an open file, so your General keeps the enemy General off every point of its file while nothing stands between them. Chinese players call using it this way borrowing the General's strength (借帅力). It costs you nothing, because the General does not even have to move.

Walking the General home: a worked example

Here is a position we checked move by move with our rules engine. Directions are from Red's side. Black's General has wandered up to the front-left corner of its palace, the corner nearest the river. Black is well ahead on material, with a Chariot, a Cannon and a Horse, but all three are far away on the right-hand side of the board.

Red has three pieces that matter. Its General is at home on the central file, and the central file is empty all the way up the board. A Red Soldier has crossed the river and stands on Black's river bank, on the same file as the Black General and two points away from it. Red's Chariot is far behind the Soldier on that same file, back on Red's side of the river.

First check. The Soldier steps forward and now stands directly in front of the General. The General cannot take it, because the Soldier is outside the palace. It cannot step sideways onto the central file, because it would be facing Red's General down an open file. The engine confirms that its only legal move is to retreat one point, to the middle of the palace's left file.

Second check. The Soldier steps forward again, into the palace, and stands right next to the General. This time the General could reach it, but Red's Chariot now looks straight up the file at the Soldier's point, so taking the Soldier is illegal. The central file is still off limits. The only legal move is back to the palace's back-left corner.

Third check. The Soldier steps forward once more and stands in front of the General on Black's second rank. The Chariot still guards it from far down the file. The General cannot step right onto its home point, because that point is on the central file, and there is no point further back. Checkmate, delivered by the weakest piece on the board.

In Chinese notation all three of Red's moves are written the same way: 兵六进一, Soldier on the sixth file forward one, played three times. Black's extra Chariot, Cannon and Horse never get a useful move, because every Black move was forced.

Take one helper away and it fails

It is worth testing the pattern by removing its supports, because that shows you what to look for in your own games.

Remove Red's Chariot and play the same moves. The first check still works, but on the second one the General simply takes the Soldier, which no longer has a guard. Now put the Chariot back and move Red's General to the back-right corner of its palace, off the central file. This time the very first check fails, because the Black General steps sideways onto the empty central point. Our engine confirms both. Each helper has one job, and without it the chase is over.

Other shapes of the chase

The chase does not have to run straight up a file. A Soldier that has crossed the river can also check from beside the General, so it can push the General sideways along a rank as well as back toward its home. The rules of the pattern stay the same: guard the Soldier, cover the escape points, and repeat.

The guard does not have to be a Chariot either. A Horse can guard the next point the Soldier will step to, and a Cannon can do it from behind a screen, but both need care, because every Soldier step changes which point needs guarding. A Chariot or your own General sitting on the Soldier's file is the simplest helper, since it guards every point the Soldier walks through.

Using the pattern in your games

The chase works best when the enemy General has already left its home point, often because earlier checks have pushed it up the palace. A General on the front rank of its own palace is a warning sign, and a Soldier nearby is the piece to bring in.

Before you start, count the jobs. One piece must guard each point the Soldier will check from, and every sideways step must be covered. Your own General on the central file covers a lot of them for free. If a check would leave the enemy General two ways out, stop and look for the preparing move first.

Be careful not to push the Soldier too early. A Soldier can never move backward, and once it reaches the last rank it can only step sideways. A Soldier that races to the back rank before the mate is ready has used up most of its power.

On defence, the answers follow from the same list. Keep your General at home when you can, keep the points beside it covered by your own pieces, and trade off whatever is guarding the Soldier's file. An unguarded Soldier that walks into your palace can simply be captured.

Practise the chase

Soldier mates are easy to miss because nobody expects the smallest piece to finish the game. XiangqiPlay's 5,000 engine-proven mate puzzles at /puzzles include plenty of them. Once the pattern feels familiar, create a free account and play the computer at any of its eight levels, from Easy to God, and keep an eye out for a General that has climbed away from its home point.