Heaven and Earth Cannons is one of the most imposing double-cannon mates. The name says it all: one cannon in heaven (the centre file), one on earth (the back rank), squeezing the palace from both directions.

1. The structure

Two parts:

  • the heaven cannon — on the centre file, facing the general, closing the route into the middle;
  • the earth cannon — on the opponent's back rank, attacking from below and threatening the general's flank.

The two cannons point in opposite directions and support each other, so a single defending piece can rarely handle both.

2. Conditions

  1. The centre cannon can hold its post, without being chased off or traded;
  2. The back-rank cannon can stay there, without being captured;
  3. Supporting pieces (chariot, soldier) can exploit the gaps the cannons create;
  4. The defender's advisors and elephants are incomplete, with no way to plug the holes.

3. A typical sequence

  1. A red cannon goes to the centre file facing the black general;
  2. The other red cannon drops to Black's back rank, pinning the flank;
  3. A red chariot or soldier checks in the gap: the general cannot go up because of the centre cannon, and cannot move sideways because of the back-rank cannon — mate.

The order: the two cannons seal top and bottom first, the other pieces close the mouth.

4. How to defend

  • Harass the cannon squares with chariot or horse;
  • Keep advisors and elephants intact so the general has spare squares;
  • Trade a cannon off — the mate needs both;
  • Keep the general away from the centre file, the natural meeting point of the two lines.

5. Why it matters

The pattern can appear in the opening, middlegame and endgame, and is at its strongest once the general has been pushed to one side and the advisors have been worn down. It is close in spirit to the Iron Bolt; the difference is that the Iron Bolt is cannon plus chariot, while this is two cannons working top and bottom.

How to practise: set up two cannons against a lone general and mate in the fewest moves, then add advisors for the defender and work out how to break the defence first.

Read next: the double cannon and Iron Bolt guides.