Honinbo Dosaku - Theoretician

Theoretician

Dōsaku is also well remembered for his contributions to go theory. He took advantage of overconcentration also known as korigatachi, making that henceforth one of the key theoretical errors that players avoided. Tewari analysis, a systematic if rather tricky tool of analysis of efficiency of sequences, is also attributed to him; as is the strategy of amashi.

In playing Peichin Hamahika from the Ryukyu Islands, in 1682, he gave a practical demonstration of his theories, winning easily when giving a four-stone handicap. This game is a textbook piece and is still frequently cited. (The first game he won by 14; the second game on the same day was also recorded and he lost by a small margin, which may naturally mean that he had nothing to prove and was being diplomatic.)

In the field of joseki, he innovated with the three-point low pincer, a more strategic play than the two-point low pincer favoured in particular by the players of the Yasui house.