Do soldiers promote in xiangqi? No. What a soldier can do on the last rank, why the old soldier (老兵) is weak, and why advanced soldiers still win games.
No. Soldiers never promote in xiangqi. A Soldier that reaches the far edge of the board stays a Soldier for the rest of the game. Because it can never move backward, and forward now leads off the board, its only moves from there are single steps left or right along that last rank.
Chess players expect the opposite, since a chess pawn that reaches the last rank turns into a queen or another piece. Xiangqi has no such rule, and it has no double first step or en passant either. A Soldier's value comes entirely from where it stands, which is why the same piece can be nearly useless on one point and decisive on the next.
A Soldier's three stages
Every Soldier, written 兵 for Red and 卒 for Black, goes through three stages. On its own side of the river it has one move, a single step straight ahead. A Red Soldier on e4, for example, can only go to e5.
Once it crosses the river it may also step one point sideways. A Red Soldier on e6 has three moves, to e7, d6 or f6. It still never retreats and never moves diagonally.
It also captures exactly the way it moves. A chess pawn captures diagonally, but a xiangqi Soldier takes whatever enemy piece stands on the point it steps to: straight ahead before the river, and straight ahead or to either side after it.
On the last rank it is down to two. A Red Soldier on c10 can only step to b10 or d10. Chinese endgame writing calls a Soldier in this position a 老兵 (lǎo bīng, old soldier) or 底兵 (dǐ bīng, bottom soldier). The books grade crossed Soldiers by height, from high Soldiers (高兵) through low Soldiers (低兵) down to the bottom rank, and the old Soldier sits at the bottom of that scale in every sense.
Why the old soldier is weak
The enemy General lives in a palace three ranks deep. From the last rank a Soldier can only touch points on that rank, so it can never again attack the two upper ranks of the palace. A General that stays on those ranks has nothing to fear from it.
The clearest test is the simplest endgame there is: a General and one Soldier against a bare General. Running every legal placement of those three pieces through the rules engine behind XiangqiPlay gives a clean answer. With Red to move, every position in which the Soldier had not yet reached the last rank was a forced win for Red. With the Soldier on the last rank, not a single position was. The defending General just shuffles along the upper ranks of its palace, and the old Soldier can do nothing about it.
That is why careful players rarely rush a Soldier all the way down. One rank higher, the same piece still attacks points inside the palace and still has useful squares to go to.
What an old soldier can still do
Weak is not the same as useless. From the back rank a Soldier still covers the points beside it, so a Red Soldier on c10 takes d10, a corner of Black's palace, away from the enemy General. It can capture an Advisor or Elephant standing next to it on that rank, and if the General itself drops to the back rank beside it, the Soldier gives check.
It can also serve as a screen. Any piece of either colour can be the platform a Cannon jumps over, and a Soldier parked deep in enemy territory is a screen that is hard to remove. In endgames where heavier pieces are still on the board, these small jobs can matter.
Why advanced soldiers still win games
Before it reaches the bottom, a crossed Soldier is one of the most stubborn attackers in the game. It cannot be driven back, since it never moves backward anyway, and near the palace it takes away points the General needs. Even when it is not threatening mate, it can tie a defender to one spot for the rest of the game.
The lone-Soldier win shows how little it needs. Put Black's General on d10, a Red Soldier on e9 and Red's General on f1, with Black to move. The Soldier covers e10 straight ahead and d9 beside it, so Black's General has no legal move at all. It is not in check, but in xiangqi a player with no legal move loses, so the game is over.
Two Soldiers can mate directly. With Black's General on e10, Red Soldiers on d9 and e9 and Red's General on f1, the Soldier on e9 gives check. Black cannot take it, because the Soldier on d9 protects it from the side. That same Soldier covers d10, and f10 would leave the two Generals facing each other on the f-file. It is checkmate. Remove the Soldier on d9 and Black simply captures on e9, which is why Soldiers are strongest in pairs.
Notice the quiet helper in that second position. Red's General never moves, yet by standing on the f-file it keeps Black's General off f10, which is the flying general rule turned into an attacking weapon. Soldiers and the General work together in a great many endings.
The named patterns build on these ideas. Eunuch Chasing the Emperor: Xiangqi's Soldier Checkmate shows one Soldier driving the General back with checks while other pieces cover the escape points, and Two Ghosts Knocking at the Door in Xiangqi (二鬼拍门) shows two Soldiers freezing a General on its home point.
Practical rules for your Soldiers
Push Soldiers with a purpose and keep them together, because two connected Soldiers protect each other in a way a lone runner cannot. Stop a rank or two short of the bottom unless going all the way wins something concrete, such as an Advisor or a mate. When defending, deal with an enemy Soldier before it reaches your palace, and once it has become an old Soldier, it is usually far less urgent.
Count the cost of every step, too. Each Soldier move is a move not spent on a Chariot or a Horse, and a Soldier can never come back to help if the game turns against you. Early in the game, Soldier moves are usually about making room for the Horses and controlling key points, not about racing for the far side of the board.
To see these ideas in your own games, play the computer on XiangqiPlay at any of its eight levels from Easy to God, and look for Soldier finishes among the 5,000 engine-proven puzzles at /puzzles. A free account is all you need to play.
XiangqiPlay Team
XiangqiPlay newsroom
