From ArimaaWiki

After five rounds of the Open Classic, the World Championship Finals will began the weekend of February 14-15, 2009. There are four games in each of the first two rounds of the 2009 World Championship Finals, identical to the format of the 2008. The tournament is Double-Elimination with players paired against opponents with the same number of wins, using a "folding pairing" system.

• Final rounds: 2009 World Championship Finals, Rounds 3+
• See also: 2009 World Championship for tournament overview and Open Classic section

Contents 1 Round 1 1.1 99of9 vs. Adanac 1.2 camelback vs. chessandgo 1.3 The_Jeh vs. arimaa_master 1.4 Fritzlein vs. Tuks 2 Round 2 2.1 Adanac vs. chessandgo 2.2 arimaa_master vs. Fritzlein 2.3 Tuks vs. The_Jeh 2.4 99of9 vs. camelback 3 Results

Round 1

Players are matched by folding pairing, using the order of finish in the Open Classic: 1 versus 8, 2 versus 7, 3 versus 6 and 4 versus 5. The top seed in 2008, Fritzlein, won the entire tournament. This time around, it's chessandgo who gets the privilege of having the inside track in the Championship Finals.

99of9 vs. Adanac

Both players opened aggressively on the east side, with a double Elephant + Horse attack on the wing. Adanac broke off his attack and pulled a rabbit to h3 after the gold camel shifted to f2. On the 7th move, 99of9 used his western horse to threaten a rabbit pull while the silver elephant threatened to frame the eastern gold horse. The horse was able to avoid the frame with help from its camel, and then on move 10g the gold camel itself advanced into the northeast, joining a heavy concentration of pieces. On the 12th move, the western gold horse continued pulling a rabbit to a5, while a silver horse escaped the northeast traffic and attacked the southeast trap (careful to ensure the gold camel couldn’t pursue to the south!) On the 14th move 99of9 made a crucial error that lost a rabbit and temporarily removed his elephant from active play.

The gold elephant became partially blockaded on the f7 square on 16s, leading to a larger positional advantage for silver. With 20g, 99of9 was able to briefly regain material equality by capturing a silver rabbit in the southwest. A move later he had to sacrifice a dog, however, as there was a goal threat in the east and his horse used 4 steps to share control of the f3 trap. Adanac captured the dog on 21s and then started to build a second goal threat in the west. With goal threats on both wings, 99of9 had to sacrifice a few pieces to delay the goal threats and, after some tough resistance, a silver rabbit scored on 29s.

camelback vs. chessandgo

Camelback opened the game with a couple of attempts to pull the silver horse out of the northeast corner with his elephant. Chessandgo brought his horse to safety and then sent it into the southeast for a rabbit-pulling mission on 6s. Camelback used his 10th and 11th moves to march rabbits north on the western flank, giving him advanced rabbits on both wings. The gold army was not able to infiltrate into any of silver’s key defensive squares (b6, c7, f7, g6) and so his advanced rabbits soon became endangered with virtually no chance to save them all. Chessandgo captured both advanced western rabbits on 17s and 19s and then the gold elephant gave up a framed rabbit in the northeast on 21g, giving silver a material advantage of three rabbits.

Silver then began a rabbit advance of his own on the western wing and used his eastern horse to aid the advance of his h4 rabbit. A gold horse was first framed, then transferred to a hostage position on b7 on 24s. A silver rabbit was framed on 26g and then immediately sacrificed reducing silver’s advantage to 2 rabbits. However, in the ensuing exchange on moves 28 and 29, chessandgo captured a dog and horse in exchange for just a horse, extending his material lead. In the next phase, a silver dog advanced in the southeast, replacing the recently-captured silver horse, and quickly taking control of the trap with the aid of the elephant. After clearing a path for the silver rabbit, it marched to victory on move 38.

The_Jeh vs. arimaa_master

After a series of pulls and retreats by both sides, The_Jeh succeeded in pushing a silver horse offside to g4 on move 9g. The gold elephant briefly held the horse hostage at h3 before releasing it, and allowing it to pull a rabbit north on 12s. The gold elephant once again froze the horse, this time on the h4 square, after which arimaa_master semi-blockaded the g4 gold elephant with a swarm of pieces to the north and the silver elephant on f4. The gold elephant escaped the swarm via the f3 trap on 16g and the silver horse immediately seized the opportunity to claim the g3 square for itself. The gold elephant once again took the silver horse hostage, this time on the g2 square, on the 18th move. After the silver elephant froze a gold horse on the e4 square with 19s, The_Jeh released the silver horse hostage to free his own horse.

With the g3 square now vacant, and with the gold elephant unable to return there due to the risk of a swarm, arimaa_master now began a series of moves in which he dominated the southeastern trap and created several positional threats. With no gold piece on the e2 square on the 22nd move, the silver elephant was able to clear the f2 square for the silver horse, thus setting up a frame threat on the f3 trap. On 24s, a gold horse was framed on the trap square, giving arimaa_master a very powerful position. Not only did the silver elephant rotate away from the frame on 26s, it did so with an immediate threat against the gold camel. The_Jeh sacrificed his framed horse in an attempt to save the camel, but he lost both strong pieces in exchange for only a rabbit. In the hopeless position, the gold elephant hurled itself upon the f3 trap, and silver won shortly thereafter on 32s.

Fritzlein vs. Tuks

Fritzlein opened the game with a quick Elephant + Horse attack in the northeast corner on 4g. Tuks responded wisely by blocking out the f7 square and holding his horse on g6. The gold horse moved to h6 and the camel joined the attack on move 8g, attempting to clear the crucial g6 square for the horse. The silver elephant parked on the f5 square in an attempt to stop the camel’s advance. However, a gold rabbit advanced to h5 on the 9th move, enabling the camel to get the gold horse onto g6 two moves later. The silver horse returned to g6 with move 12s, framing the gold horse on the trap square in the process. However, the gold camel threatened to break the frame by advancing to g5 on 13g, supported by a dog on f4 which prevented the camel from being flipped to e5.

Fritzlein gained a large advantage on the 15th move, returning his horse to the powerful g6 square while also being in a strong position to pull the silver straight south with the camel. The attack continued in the northeast on 17g as the elephant flipped a cat to d6, creating a threat against the exposed dog on f7. Tuks made a crucial error on 17s by placing his elephant on his trap square rather than moving his dogs to f6 and f7. An unstoppable threat came as a result because now the silver horse, which had been pulled all the way to h3 could not be saved without abandoning the f6 trap. The silver elephant saved the horse, giving up one of his dogs instead. After the capture of a silver rabbit on 21g, Tuks overlooked a goal opportunity on 21s which allowed Fritzlein to win immediately on the next move.

Round 2

The spectators correctly predicted every game in the 1st round, though the games were much shorter than expected. All the games lasted between 22 and 38 moves, but the predictions generally went into the 40s and 50s. There are two matchups of undefeated players in the 2nd round, (1) chessandgo versus (5) Adanac and (2) Fritzlein versus (3) arimaa_master -- both games are re-matches from the Open Classic. The other two games will see the losing player eliminated: (4) 99of9 versus (8) camelback and (6) The_Jeh versus (7) Tuks.

Adanac vs. chessandgo

The opening phase was a rabbit-pulling contest with chessandgo achieving his pull much faster. After Adanac left his rabbit exposed on g2 on move 5, it was pulled north with the silver elephant having an extra step available to box the gold elephant out of the g5 square. The gold elephant pulled a silver rabbit to g6, but was then forced to retreat to the weak h4 square. The gold rabbit was captured on move 8 while the silver rabbits were still close to home, though a parital-elephant blockade would have been a viable alternative: for example, gold rabbit on g5 and silver elephant on h4, or with the silver elephant on g4 and a wall of pieces to block out g5. Having escaped potential difficulties, the gold elephant then moved to f5 on 9g, dragging rabbits south to g5 and h5. A silver rabbit was eventually framed on the f3 square on 11g, supported by the silver elephant on e3. Silver was determined to keep the rabbit alive while using the camel to dig on the east side. Unwilling to allow the camel to advance along the h-file, the gold elephant briefly gave up the f4 square on 14g. A silver dog then occupied the f4 square on 14s, giving the framed rabbit an extra bit of support. The gold elephant did not immediately re-claim the square, as two steps were used by gold to block off the silver camel with a small wall of silver rabbits on g4 and h4. The silver elephant rotated away from the f3 trap on 16s, leaving a pair of dogs to protect the silver f3 rabbit. Gold immediately took control of the trap with his elephant, leaving the framed rabbit doomed to capture. Being at a positional disadvantage in the east, but possessing two horses in the west, chessandgo began a new attack with his elephant and horses, quickly threatening to frame the gold horse.

Adanac pulled a dog south, finally capturing the framed rabbit and shifting the gold camel west to assist against the aggressive silver horses. Chessandgo was able to achieve a brief gold horse frame on c3, nonetheless, and the gold elephant had to come to the rescue. With all the strong gold pieces on the west side (except for a horse that was out of the action at h3), the silver dogs attacked the southeast trap, followed by the silver camel on 21s which framed a dog onto f3. By this point, the advantage was clearly beginning to shift in silver’s favour. Though the gold elephant was able to save the framed dog, and the gold camel was holding 2 horses hostage, the silver position had fewer weaknesses and both gold traps were under shared control. Chessandgo began to press his advantage by first threatening the gold camel on 22s. Adanac moved his camel one step south to safety, but then left his horse on d3. The silver elephant moved to e4 on the 24th move, threatening to frame the dog on f4, but more importantly, endangering the gold horse which had been pulled to d4. Adanac made a likely error on 24g, sacrificing his cat to save the horse. Advancing a rabbit to d3, the horse to d5 and camel to b3 may have been a stronger move. After the silver elephant pushed the gold cat into danger on the c5 square, the other gold cat responded by advancing to save its partner, leaving 2 gold cats at b5 and d5. That 25th move was a compounding error, as gold might have tried to pull the silver dogs west, clearing f2 for the gold dog on moves 25 & 26, rather than exposing a 2nd cat to danger.

From that point onward, chessandgo completely dominated the board, threatening multiple gold pieces in the northwest with one silver horse while neutralizing the gold camel, freeing the other silver horse to attack the southwest. A gold cat was captured on 28s quickly followed by a dog capture on 29g. Though Adanac had a brief material lead, chessandgo dominated the board and was able to convert his advantage into a strong rabbit on the a-file. A gold horse was then captured in exchange for a silver dog on moves 31s and 32g, giving the 2 players roughly material equality. However, the gold position was hopeless due to many hanging pieces and a menacing silver rabbit on a5. Silver forced goal-in-one with 33s and then scored a move later. Chessandgo improves to 2-0 and will play the winner of Fritzlein versus arimaa_master.

arimaa_master vs. Fritzlein

After the six moves, Fritzlein was threatening both an Elephant + Horse attack in the southeast, and poised to flip the gold camel up to d4. Arimaa_master precluded both threats by bringing his elephant back to the f4 square. The silver elephant then switched over to the west side, briefly holding a gold horse hostage at b5 with 10s. When the gold elephant came to the rescue of its elephant, the eastern silver horse commenced with a rabbit pull. On 15s, Fritzlein began another Elephant + Horse attack, this time in the southwest quadrant. The silver attackers succeeded in occupying the key b3 and d3 squares on move 16 but the gold horse was also able to grab the b6 square as a result. Arimaa_master advanced his camel to c4 on 18g, after which Fritzlein abandoned his attack while pushing the gold camel to d4. The action moved north on 19g, with the gold elephant claiming the d6 square, threatening both the c6 silver dog and creating a long-term threat against the frozen e6 dog. A silver horse took control of c5 on 19s to protect the c6 dog while two gold rabbits were moved to awkward positions on the 5th rank. Gold’s next move created a double-threat as the silver dog was shoved into great danger at e4 while, surprisingly, a goal-in-one threat suddenly existed up the d-file. Silver defended against the goal threat and set up a threat against the b6 gold horse. After the gold horse fled for safety, the silver elephant was able to save the dog with 21s. Once again, the silver dog was pushed to danger, this time to e3. Fritzlein decided to give up his dog in exchange for two gold rabbits on the 22nd move, allowing him to reclaim the b6 square for his horse, and leaving the gold horse out of play at a6.

The action then shifted to the east as the silver camel pulled a gold horse up to g4. Though the gold elephant was easily able to save the horse, the sequence of moves gave the eastern silver horse enough time to grab hold of g3. That forced the gold elephant into double-duty, defending the southeastern trap and protecting the gold horse from the silver camel. Fritzlein then advanced a rabbit to h3 on move 27, adding another threat to the mix. Arimaa_master shifted his dog to g3 and camel to f3 on the 28th move, both creating a strong wall against the advanced rabbit and threatening to dislodge the silver horse from g3. However, with the gold camel in the east, the western silver horse launched yet another attack against the now lightly-defended c3 trap. Three small gold pieces worked together to defend the southwest trap on 29g, while the gold horse stepped onto b6. Gold’s 30th move appeared to solidify his western flank, as the eastern gold horse trotted over to c4 to neutralize attacking silver horse. However, it may have been an error to place the gold elephant rather than the rabbit on the f4 square, as the empty f5 square provided the silver camel an easy path to the west. When the silver camel reached the c4 square on 32s, it had a devastating effect on the gold position: both gold horses were in danger and silver had a strong grip on the c3 trap. Arimaa_master had to abandon his f3 trap in order for the elephant to intervene on the western half. Yet, Fritzlein still had time to capture a cat in c3 before the elephant could arrive. The gold pieces were able to blockade the e2 square on 35g, thus preventing the capture of the framed f3 gold rabbit. The silver cat flipped the framed rabbit to g4 on 35s in order to expose the gold camel to direct capture on the next move. Arimaa_master ignored the threats to his position in an attempt to advance that g4 rabbit as far as possible. With his 37th move he was able to advance the rabbit to g5, with few defenders in its path. Fritzlein retreated his cat to the g6 square on 37s, halting the gold rabbit. Two moves later, silver won when gold ran out of time. With his victory, Fritzlein improves to 2-0 and will face the top seed, chessandgo, in the 3rd round.

Tuks vs. The_Jeh

The_Jeh began pursuing the gold camel in the southeast with his 6th move. But the silver elephant moved back to middle after the gold camel retreated to g2 and the silver camel was threatened with a flip to d5 – retreating wasn’t as simple for the silver camel because a gold horse advance to c7 would have been possible with a vacant d7 square. With both camels secured, Tuks used his western horse to pull a silver rabbit down to a6 on 9g. The silver elephant was able to push the gold offside to b5 with 10s, though the dog had a clear path down to safety at d3. Silver achieved a rabbit pull of his own, getting a gold rabbit to b3, but with the silver elephant far away on b5, the gold camel began to harass the eastern gold horse on 12g. The silver horse escaped to safety, with the aid of the elephant, on 13s and then the gold camel was frozen and threatened. Once again the gold camel moved to its g2 sanctuary while both elephants threatened an enemy horse. The horses were exchanged on move 16, leading to a roughly level position with a slight initiative for gold. Tuks pulled a silver rabbit into a hostage position at b4, but then got into difficulty in the east when his dog was threatened with a frame. The gold camel attempted to free the framed dog on move 22, but the intended rescuer was flipped over to e5. Gold then used the next move to capture the hostage silver rabbit. With 24g, gold set a trap where he could have sacrificed his framed dog in exchange for pushing the silver camel to c4. The_Jeh saw the threat and moved his camel to b6, pulling the gold horse to b5 in the process.

Gold’s 25th move, advancing the gold camel to d6 to save the hostage b5 horse, was very risky and quickly landed him in great difficulty. When the silver elephant moved to d5, Tuks did not have enough time to both retreat his f6 dog to f4 and occupy d6 with his elephant. Gold’s best option on 26g may have been to move the camel to c7 while pushing the silver rabbit to c6, though he still would have faced great difficulty. In actuality, the f6 gold dog was sacrificed on 27g in order to save the horse and camel. The gold camel then moved into a fairly strong position at f7 on move 29. Tuks used his camel and elephant together to push silver pieces away in a bid to clear a path for the advanced gold rabbits. In the meantime, The_Jeh worked his elephant to f5 and then later pushed gold dog into grave danger at d6 on 32s. Down two dogs at that point, Tuks advanced his rabbit to h7 and then tried desperately to advance it one more step. However, the silver army had more than sufficient pieces on the two home ranks to clog up the position and thwart gold’s hopes. Resistance effectively ended on 36s when the gold camel was framed on the f6 square on 36s. The silver pieces soon took control of the whole board, capturing a gold rabbit on the 42nd move. Tuks sacrificed his camel in order to activate his elephant but that also had the effect of activating a flood of silver pieces on the east side. A silver horse, dog and rabbit then advanced into the southeast and the rabbit reached the f1 square on 48s.

99of9 vs. camelback

The start of this game was delayed for a couple of days as 99of9 and camelback had difficulty arranging a time to play. Technically, 99of9 could have won by forfeit as camelback couldn’t play at the originally scheduled time but, continuing the fine Arimaa tradition of good sportsmanship, the game was re-scheduled instead. The two players opened the game with differing philosophies, as gold pulled a silver rabbit down the f-file while silver began an invasion of the west side with an elephant, camel, horse and rabbit. Camelback advanced his horse to c3 on 9s and threatened to occupy a powerful position at c2 but 99of9 blocked the horse out with four smaller pieces. Unable to make further progress, the silver pieces then reverted to their previous positions on move 10s, with the horse returning to c4, rabbit to c3 and the elephant to d3. While the silver pieces attacked the southwest, a gold camel, horse and rabbit began inching forward on the east side. The camel pushed the silver horse off the g6 square on 12g which then prompted camelback to give up his c3 rabbit in order to break up the gold counter-attack with his elephant. The gold camel was able to retreat safely back to g3, thanks to the advanced h5 rabbit. Having stopped the attack in the east, the focus immediately reverted back to the southwest where 99of9 was threatening to win a second silver rabbit on move 14.

With a replacement silver rabbit occupying the c3 square, camelback once again returned his elephant to d3 and horse to c4. This time around 99of9 had more issues to deal with in the southwest as the gold elephant was keeping the silver camel at bay at a4 while a small swarm of silver pieces were pushing into the south. The gold elephant dealt with the situation by pushing the silver camel north on 17g and giving the b4 square to the gold horse. Camelback rotated his elephant away from the d3 square, which turned out to be a disadvantageous move after the gold horse seized the c4 square, leaving the silver rabbit framed on c3 and supported only the horse on d3. The weak frame could have been destroyed by the gold camel on 19g, but only at the cost of its life on 19s. Instead, 99of9 used one step on his 19th move to block out the e2 square, and then captured the framed rabbit on 20g. This led to a complex series of moves by which the gold camel was doomed but silver also had various pieces exposed to various degrees of danger. A silver cat was captured on 21g, resulting in a brief material lead of a cat and 2 rabbits for gold. Camelback missed a great opportunity on 22s, as he could have captured the gold camel while using his other 2 steps to place his cat on c4 (thus saving his own camel). When he missed that tactic, it led to an exchange of camels instead. However, silver still had positional strengths and a gold cat was pulled into f3 by a strong horse which then occupied g3 on move 23s. A gold rabbit was captured a couple of moves later, reducing 99of9’s material lead to a single rabbit.

Both eastern silver horses retreated north and then on move 28g, the gold elephant began to pursue both of them. The silver elephant responded by chasing the western horse, which led to an exchange of horses on move 30. Nine pieces had been removed from the board at that time, and so both sides began to play more aggressively. When a silver dog threatened to occupy b3, the gold horse moved west in response. However, the silver elephant then pushed the horse north, freezing it on d4. After some tactical shuffling by gold to save his horse, a gold dog was captured on 35s. This gave camelback a brief material lead (each side had 11 pieces, but silver had an extra dog in exchange for an extra gold rabbit), but gold had powerful threats on both sides of the board. The silver elephant could have saved the hostage silver horse on move 36 but that would have left the gold horse in a powerful position to either threaten the silver dog or help advance gold rabbits in the west. Camelback chose to capture another rabbit in the west instead, and after 99of9 captured the hostage horse, he was ahead by a horse for a dog. Now only 20 pieces remained on the board, 12 of which were rabbits.

The gold dog seized the strong g6 square on the 41st move but a silver rabbit was able to defend the square by advancing to f5. It was also a menacing location for the rabbit, as gold’s southeast quadrant was occupied only by 3 rabbits. When 99of9 threatened the menacing rabbit, the silver elephant shifted east to protect it. But when the gold horse stepped up to b4, as the dominant western piece, the silver elephant moved back west. Gold abandoned the idea of capturing a silver rabbit in the f3 trap, and instead pursued a new strategy of advancing a rabbit to h6, supported by a strong dog on g6. Camelback captured another gold rabbit on 46s, but that allowed 99of9 enough time to advance the dog to g7 and rabbit to g6. When the gold elephant and dog inevitably dominated the northeast trap, the silver elephant was essentially forced into leaving the gold horse alone in the west on 48s. That horse then worked quickly to capture a silver rabbit and then occupy b6. The silver elephant shuttled back to the west once again, this time creating the threat of a silver rabbit advance along the b-file on 52s. 99of9 prudently blocked that potential advance, and then developed a powerful rabbit of his own on e4. A move later, camelback captured a gold rabbit but in doing so overlooked a goal-in-one by 99of9. The gold rabbit marched to victory, ending the great struggle on the 55th move.

Results

Seed	Participant	Rd. 1	Rd. 2
1	chessandgo	S 8 W	S 5 W
2	Fritzlein	G 7 W	S 3 W
3	arimaa_master	S 6 W	G 2 L
4	99of9	G 5 L	G 8 W
5	Adanac	S 4 W	G 1 L
6	The_Jeh	G 3 L	S 7 W
7	Tuks	S 2 L	G 6 L
8	camelback	G 1 L	S 4 L