2006 Challenge Match
Given his former difficulties persuading top humans to defend the Arimaa Challenge, Omar Syed changed the format beginning in 2006. Instead of a single human playing a two-week, eight-game match against the top computer, three humans would each play a three-week, three-game mini-match, alternating games. The computer would need to win two out of three games in all three mini-matches to win the Challenge. Syed intended to relieve the psychological pressure and time commitment required of volunteer defenders. The changed format also recognized that an increasing number of human players were capable of beating any bot.
The human participants in 2006 Challenge were Karl Juhnke, Greg Magne, and Paul Mertens, ranked first, second, and sixth respectively. The human contingent was supremely confident entering the match, not only based on the results of past years, but also because the year since the previous Challenge had seen the development of half a dozen different strategies for reliably exploiting computer weaknesses. Mertens, in particular, had beaten the 2005 version of Bomb with a variety of enormous material handicaps.
Unbeknownst to the defenders of the Challenge, the computer challenger was the exact version of Bomb from the previous year. Perhaps the humans were fooled by ease with which Bomb won the 2006 Arimaa Computer Championship, against supposedly improved competition.
In any event, humanity swept the first eight Challenge games, and in six of those games did not lose a piece. Only in the fifth game of the match, against Magne, did Bomb generate winning chances, but Magne rose to the occasion and punched a rabbit to goal where Bomb had left too thin a defense.
For the ninth and final game, Mertens decided to test the margin of human dominance by offering Bomb a material handicap of a camel. In theory, playing without a camel should render all modern strategies ineffective. Mertens was unable to gain control of the game, but did generate a sharp goal race, which Bomb won by a narrow margin.
The final score of 8-1 in favor of humanity reflected the widening gap between humans and computers in Arimaa ability. In all likelihood the Challenge could have been handily defended by the humans ranked eighth through tenth because the techniques required to defeat Bomb with predictable ease had been mastered by all the top players.
