Arimaa/Attacking/Attacks Against a Camel Trap
When a camel is decentralized at home, the opponent might attack either trap. The trap not defended by the camel could be vulnerable, but the camel trap might be a good target also, as an elephant prefers to be near the enemy camel. A strong attack against the enemy camel trap could force the enemy elephant to defend its camel; much like a camel hostage, such an attack could make one's own camel the strongest free piece. If the defending camel took a strong hostage, however, such an attack could backfire badly; the attacking elephant could be stuck defending the hostage while the enemy elephant was free. Such attacks are sharp, and the whole board must be considered.
It is easier to attack against a camel which is not supported by a friendly horse. Without a supporting horse, a camel may have trouble holding a key square (and potentially keeping a hostage): a weak piece in front could be pulled away by any piece stronger than itself, and then the camel could be vulnerable to the elephant. With this in mind, such attacks are commonly employed against setups which place the camel on one wing and both horses on the other.
Eventually, the defending camel could be at risk of capture. An attacker might push the defending camel toward his home trap and thereby create threats in both traps. That could be a strong move, although decentralizing one's elephant in enemy territory is often risky.
Boo vs. chessandgo
Before 2g: Silver attempts to exploit Gold's setup.
This game was played in the 2013 Arimaa World Championship. Gold used an HH setup; Silver then set up with his camel directly facing Gold's horses, and his dogs facing Gold's camel on the other wing. The silver dogs can advance along with their elephant, as the gold camel would waste its strength fighting dogs and likely could not even keep a hostage. With such a strong alignment, Silver might attack on both wings. Gold has no clear prospect for an attack on c6 or f6, as Silver is likely to get a strong hostage if the gold camel advances in the east or a gold horse advances in the west.
Before 6g: Silver prepares an eastern attack.
- 6g Ed6s cd7s Ed5e cd6s. Gold moves his elephant toward the coming eastern fight, pulling along a silver cat which he hopes to capture before Silver's attack is far advanced. Given what follows, the cat pull was probably a mistake.
- 6s De3w ee4s dg6s rg8s. Silver moves toward a multi-piece attack on the f3 trap, and threatens to begin captures immediately. If the gold camel steps forward to defend, it will risk being pushed or pulled toward f6.
- 7g cd5s Ee5w Mg2n Cf2n. Gold advances both the camel and cat, occupying f3 to delay Silver's attack. The silver cat faces a one-turn capture threat in c3.
- 7s hf5s hb6ss mb7s. The eastern silver horse threatens to push through to f2 (pushing the gold cat onto g2 so the gold camel couldn't immediately take the horse hostage) or flip the gold cat to f5. Both gold dogs are now frozen, so the silver cat cannot be captured.
Before 10s: Silver has an unusually strong cat on f2.
- 8g Rf1n Mg3n Rh3w Cc2e. The gold camel freezes the attacking silver horse and dogs, while two gold rabbits now defend the f3 trap.
- 8s Dd3w ee3w cd4es. The silver cat escapes, and joins the attack on f3 while the silver elephant defends c3. It is unusual for a cat to be such a strong attacker in the opening, but the alignment leaves Gold limited options for dealing with the silver cat.
- 9g Dc4ee Ed5e Rc1n. Gold could have used his elephant to neutralize the silver cat and create a threat in f3, but this would have allowed Silver to begin a race that Gold could not have won. After 9g Ed5es ce3s Ee4s 9s Dc4n hb4e Dc5nx hc4n 10g Ee3n Cf3w hf4sx Mg4w, Gold's horse-to-dog lead would have been short-lived; on 10s, the silver camel could have immediately dislodged the b3 horse and thus captured the c3 dog, while threatening further captures in the west. Gold thus opted for a 9g that saved his dogs; the silver cat remains a strong attacker.
- 9s ce3s Rf2s ce2e ed3e. Silver gets an away frame. While not yet solid, this frame presents an immediate threat since the pinned piece is a rabbit.
- 10g Rg1n Rf1e Re1e Dc3e. Gold declines another tempting move: the gold elephant could have captured the f7 rabbit in f6, where Gold would have then had follow-up threats. However, after 10g Ee5nn rf7sx Ee7e 10s cf2ew Rg3s Cf3x 11g dg5w Mg4n df5nx Mg5w 11s ee3e hf4es ef3n, Gold would scramble to avoid disaster in f3, and Silver would at least get ahead. Gold was thus correct not to go for such an attack on f6. Instead, Gold protected his framed cat and pinned rabbit by blockading g2 and occupying d3.
Before 16g: Silver has a high camel hostage.
- 10s rh8sss rg7s. By unfreezing the h4 dog, this move threatens the f3 cat, which could be the first domino to fall.
- 11g hf4n Mg4w De4w Ee5s. Gold had to break the frame, and preferred to keep his elephant in the center. A silver dog can now reach g3, however, pinning the gold camel and by extension the gold elephant.
- 11s dh4w Rg3e dg4s hb4e. Silver again frames the f3 cat. The silver horse steps east, threatening to flip the gold dog toward c6 and also making way for the silver camel to advance. Gold could now capture the silver horse, but Silver would then capture a cat and camel in return; after 12g Dd4n Ee4w hc4sx Ed4w 12s hf5w ee3n Mf4n Cf3x ee4e, the gold camel would be hopelessly forked.
- 12g Cd2s Dd3se Dd4s. Gold aims to break the new f3 frame from behind. Given Silver's next move, perhaps a step should have been spent occupying b2.
- 12s mb6ss Hb3s mb4s. Silver's camel advance renders both gold horses passive, and the silver horse now threatens to move through the c3 trap.
- 13g Cd1n Rb1e Rf1w. Gold blockades c2, and prepares to push the silver cat to f1. Gold must beware of the silver elephant moving from e3 to d3, perhaps framing a piece in c3.
- 13s hc4s Dd3n hc3e hf5w. Silver displaces the gold dog from d3, quickly moving toward a double-threat in the west.
- 14g Dd4w cf2s De2e Rh3n. Gold adds a defender to each home trap.
- 14s re8ss he5ww. Silver threatens to clean up in the west.
- 15g Ee4wn hd3n Cd2n. Gold defends in the west, but leaves his camel vulnerable in the east.
- 15s ee3n Mf4n ee4e dg3n. The g5 blockade completes a nice high camel hostage.
- 16g hc5w Ed5w Dc4w Ec5s. The gold camel cannot escape f5, and much is at stake in the west. Gold concedes the camel loss, but aims to capture a silver camel or horse in return.
- 16s re6ws Cd3w hd4s. Silver again shares control of c3.
- 17g Ec4e hd3s Ed4s Cc3n. Gold threatens the silver camel and horse, but the other silver horse is ready to defend.
- 17s hb5e Cc4s hc5s dg4s. Gold cannot regain full control of c3, and will lose it totally if the gold elephant leaves. The gold horses contribute nothing, and Gold is overloaded.
- 18g Ha3n Db4n Ha4n Cf3w.
- 18s Mf5nx ef4n rb8s rd5s. Gold loses his camel for nothing.
Gold's HH setup left him vulnerable on both wings, and Silver's double-trap attack worked perfectly. Since Silver sets up second, Silver can exploit an HH setup by Gold much more easily than Gold could exploit such a setup by Silver.
Sharp vs. Dolores
Despite a material deficit, Silver can now get a strong attack against f3 by moving the g4 dog onto f2.
In this game between two top bots, Silver initially lost a horse and rabbit for only a dog, yet successfully attacked Gold's camel trap, which was weakly guarded from behind. Once the gold elephant went east to defend its camel, the silver camel was the strongest piece in the west. The gold camel went north to defend f6 from behind, but Gold was overloaded at home.