The not-so-mighty Lion


The Lion is well known for it’s power of be able to mate a King unaided even by it’s own king. And yet two Ferocious Leopards vertically stacked, as shown above, are such a good example of perfect shape that they are invulnerable to the Lion.

The following diagram:



again shows the powerlessness of the Lion in the face of self-protecting step-movers. This position is a draw (assuming a suitable modification of the repetition rule. E.g. If at least one player has no more than 5 pieces, then repetition is allowed, and results in a draw).

Another well-known example is that the basic castle is immune to an unassisted Lion (even the assistance of the king is insufficient). I.e. this position is also a draw:


Incidentally, the way to get 81Dojo to record a draw is as follows:

  1. Both players agree it is a draw (verbally)
  2. Both players disconnect (by closing the brwoser tab/window) within 30 seconds of each other.
  3. This requires trusting your opponent (if you’re the first to disconnect). But in case you don’t know him/her well enough to trust them, simply reconnect immediately. If your opponent has not yet disconnected, reconnect to your game, and carry on.

Sacrificing the edge pawn


Consider the position above. Black’s Lion has invaded the corner. If he now plays Ln x 1b x 1a, White will reply with Ln – 3b, and the Black Lion is dead. If instead he plays P x 1f, White replies Ln – 4c, and Black’s Lion will still have no escape.

Now let’s consider a minor change on the edge:


Now the difference is slight, White has captured the edge pawn. But this is his undoing. Now Black can safely play Ln x 1b x 1a. If White continues with Ln – 3b, Black plays RC x 1g, and he is fine.

The same sort of situation occurs in the endgame when White is not trying to stop the invasion, but instead is making an attack of his own. In such a situation, Black wants to promote to get a Whale and a White Horse into play as quickly as possible. But in the first diagram, after capturing the opposing Reverse Chariot and Lance, Black will have to play an additional four Pawn/Tokin moves before he can start to promote. Whereas in the second diagram, he will just have to use one move to first capture the Pawn. Therefore the second situation is 3 moves faster for Black.

So when this sort of attack is planned, it is to Black’s advantage to sacrifice the edge pawn first. But the timing is difficult. If played much earlier, White will simply capture, and may well be able to launch a decisive attack using his edge Pawn. If left too late, Black might not have time to make the sacrifice (or capture and attack, if White declines the sacrifice).

HaChu on a new machine

For some weeks now, the 5 HaChu bots running on 81dojo are powered by a new machine. This is an Intel® Core™ i7-4770K CPU @ 3.50GHz × 8 (that’s 4 cores, each hyperthreaded), with 32 GB memory, running Linux Fedora 20. This should give the bot at least twice as much power compared with before, when it was running on a laptop. This should result in slightly longer look-ahead, and therefore stronger tactical power.

Continuation from White’s counter-foray

The last post in this mini-series on the opening resulting from Black’s early Lion foray, showed White retaliating in kind in response to Black supporting the Lion with the Go-Between. The position was this:

Black plays GB - 9g and White responds with his own Lion foray

Black plays GB – 9g and White responds with his own Lion foray

Black’s intention in supporting the Lion with the Go-Between is to follow up with a “sacrifice” of the Dragon Horse. To this end he first plays P – 5h, Ln x 4h – 4g, then plays DH x 10+, yielding this position:

Black proceeds to "sacrifice" the Dragon Horse

Black proceeds to “sacrifice” the Dragon Horse

Since the Horned Falcon now threatens to “eat” the Rook on 10c without moving, White has no choice but to capture it, so taking with the Rook is clearly best. Black then captures the Rook with the Bishop. The exchange of Dragon Horse for Rook and Pawn is about even, but the promotion of the Bishop gives Black perhaps a slight edge in material. Additionally,  his Lion is still supported in an attacking position. Therefore White does best to retaliate in kind, leading to this position:

Position after exchange and White retaliates.

Position after exchange and White retaliates.

Now the position is almost symmetrical, the only differences being that Black has advanced his Go-Between to support the Lion, and White has played the developing move of P – 5e, opening a diagonal. If Black were to now also open the diagonal with P – 8h, White would have a chance to make it completely symmetrical with GB – 4f, but why would he choose such a slow, non-developing move, when there is no need to protect his Lion? So I conclude that Black has wasted the advantage of the first move. Extensive experience in this position confirms that Black seems unable to get an advantage in this position.

The series will continue by examining the better alternative to GB – 9g, namely retreating the Lion to 7h.