What is 重炮 (double cannon)?
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
重炮 — "stacked cannons" — is two cannons on the same line as the enemy general, one behind the other. The front cannon is the screen the rear one needs, so the rear cannon gives check straight through it. It is mate when the front cannon is defended and the general cannot step aside.
The three conditions
- The front cannon is defended. Otherwise the general simply captures it.
- No gap to interpose into. The front cannon sits immediately in front of the general.
- The general cannot move sideways — usually because its own advisors occupy those points.
The irony of the pattern is that the defender's own advisors are what make it work.
Where it comes from
Most 重炮 mates grow out of an ordinary Central Cannon position: one cannon is already on the central file, and the second swings across to join it. That is why the defensive alarm is simple — if an enemy cannon is on your general's file and a second one can reach that file, count the moves before you do anything else.
Related questions
How is it different from 馬後炮?
Both use a screen. In 馬後炮 the screen is a horse that also covers escape points; in 重炮 the screen is the second cannon and the defender's own pieces block the escapes.
Can the general take the front cannon?
Only if it is undefended — which is why defending it is the first condition.
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