Arimaa/Other Hostages
Horse-by-elephant hostages
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As long as her elephant remains in the northeast, Silver can do little other than pull a gold rabbit on the a-file. |
As with a camel hostage, a horse or smaller piece hostage will be effective only if it gives the hostage-holder a usable advantage in free pieces. This is usually not the case when an elephant holds a horse hostage, as occurred in this opening. Silver's alignment is poor; the gold elephant is a far greater threat to the silver camel than is the silver elephant to the gold camel. Gold would gladly trade his horse for the silver camel, which if it came east would be at risk in both c3 and f3. If a silver horse advanced first, it could be threatened by the gold camel. If the silver elephant simply left the f6 trap, Gold would have a strong attack which might decimate Silver's eastern forces.
For now, the gold elephant is better placed on e6 than on f5. If e6 and e7 were clear, the silver elephant could pull the gold horse onto e7 and then perhaps fork it between traps. That is a possible advantage of positioning a hostage-holder behind the trap.
In some cases, a horse-by-elephant hostage might be converted to a frame or passed off to the camel. If Silver were better positioned for that, it would be urgent for Gold to prevent a solid frame or horse-by-camel hostage, which could free the silver elephant while the gold elephant remained stuck defending the horse.
Gold should be prepared to go after an aggressive silver piece or clean up in the east, but if Silver plays gingerly, Gold might swarm the f6 trap and rotate out his elephant.
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Gold cannot save both horses. |
While a horse-by-elephant hostage is usually a bad long-term strategy, it may be an effective tactic if the hostage-holder can make a quick second threat. In this opening, Silver threatened both gold horses, and Gold did not have time to defend both traps.
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Dogs will likely decide this game. |
A horse-by-elephant hostage may be effective on a depleted board. In this endgame, such a hostage tied up the three strongest remaining pieces. Up two-to-one in dogs, Silver can dominate the rest of the board. If a second gold horse or dog remained, this hostage would likely be weak.
Horse-by-camel hostages
[edit | edit source]The camel is usually the piece that should fight an enemy horse long term. This may lead to a horse-by-camel hostage, which could be very strong or very weak. The "defending" elephant can usually dislodge a hostage-holding camel, at least temporarily; what happens next depends on what other pieces are nearby. If the hostage can be held without the direct support of the friendly elephant, the hostage-holder may have a large elephant mobility advantage.
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These diagrams illustrate different horse-by-camel hostage configurations, with Gold holding such a hostage in the southwest. A gold piece is always on a4, to keep the gold camel mobile if it is pulled to b4. In the first diagram, the b2 cat allows for capture of the hostage if the silver elephant goes to b4. Gold should leave d3 clear, so that the camel could finish that capture on d3 rather than c4, where it would then be at risk in c6. The b2 cat and empty d3 square indirectly protect Gold on the b-file; if the silver elephant could afford to step west and begin the next turn on b4, things could quickly turn around. As things stand, this may be a solid hostage position for Gold, whose own elephant is the strongest free piece for the time being.
Without a gold piece securely on a4, the hostage would be weak. With ec4we Mb3n ha3e, Silver could have her elephant on c4 and her horse on b3; if the gold camel were frozen on b4, Silver would have strong capture threats in c3, and could also flip the gold camel to c5 with a threat to capture it in c6. The a4 square is thus crucial to such a hostage position, and Gold does well to have a horse on that square, as a weaker piece could be pulled away more easily.
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In the second diagram, the hostage horse is on b2 rather than a3; this has implications if the camel is dislodged. For instance, if the silver elephant moved to b4, it would then threaten to capture the camel due to false protection. On the other hand, a hostage on b2 could be pushed to b1 if the camel needed to back away from the elephant. The camel might then move the hostage to c1, or back to b2 when feasible.
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In the third diagram, the hostage is held behind the trap. On c2, the gold camel is less exposed and thus perhaps easier to support. A camel-held hostage behind the trap can thus be strong, if the area is reasonably well-fortified and the opposing army is not well-developed on the wing.
In all of these cases, the defender should consider bringing in more pieces if possible. In the last example, Silver could own the trap if she could take b3 in addition to d3. In the first, the silver camel might displace Gold's linchpin horse.
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Gold has no good way to break this hostage. |
When a camel holds a hostage behind a trap, the defender might be no better off if he pushes the camel away. In this game, Gold's 13g left him even more vulnerable in the west, where Silver then advanced a horse and dog. When the gold elephant left f7, the silver camel retook the hostage. When an elephant goes to a corner to try to free a hostage, there is also a risk that both pieces will get blockaded.
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Silver's horse-by-camel hostage allows silver dogs to control an away trap. |
By tying up the gold elephant and horse while other strong pieces were tied up in the west, Silver's horse-by-camel hostage at right enabled silver dogs to control f3. This led to a 29-turn win.
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Gold holds a camel hostage in the east, and a double hostage in the center. |
In this game, Gold's central horse-by-camel hostage allowed him to defend goal in the west, as no additional silver piece could reach the southwestern corner. This would be a strong position for Silver if he could displace the gold camel, but Gold to move can blockade c3 and perhaps move toward a northwestern goal threat. With the southern forces tying each other down, the western gold horse is the strongest free piece; the silver elephant must stay beside c3, and cannot freeze the gold horse in place. One way or another, this horse can soon accomplish something.
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Blocked by his own rabbits, Gold cannot easily displace the silver camel or horse. |
After 15s of this game, Silver in effect had a strong horse-by-camel hostage, despite the proximity to the gold elephant and camel. Advanced gold rabbits shielded the silver camel and horse. Silver kept e7 and f7 occupied, so that the gold rabbit could not get off of f6 and threaten goal.
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Silver's development allows the silver camel to hold a hostage from a5. |
After 17s of this game, the hostage-holding camel was itself on a5, and supported by silver pieces which had advanced further. Gold could unfreeze and move his horse, but couldn't really threaten the silver camel. Gold might advance more pieces toward c6, but that could further weaken his own home defense.
Cat and dog hostages
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Silver does not have an ideal alignment, but may eventually overload Gold. |
A smaller piece may also make a valuable hostage, if its elephant is the only piece which can defend it. In this game, the silver camel held a gold dog hostage behind c6. The silver elephant is free to pull gold pieces toward f6. The gold elephant can't defend both traps.
However, Silver's situation is less than ideal, for a few reasons. The silver camel does not currently threaten either gold horse. Even if the gold elephant leaves the c6 trap, Silver will have to clear space for the dog capture. Gold is well-developed in the east, and might create a double-threat on that wing. A dog-by-camel hostage is not ideal, but may still give the hostage-holder an elephant mobility advantage.
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Gold's dog-by-horse hostage allowed the gold camel to safely advance to g6. |
In this game, Gold's early dog-by-horse hostage allowed for an elephant-camel attack on f6. An early camel advance would often result in a camel hostage, but the southeastern hostage gave Gold time to advance his camel and support it with rabbits.