Drops were not originally part of shogi. In the 13th century, shogi underwent an expansion, creating the game of dai shogi, played on a 15×15 board with many new pieces, including the independently invented rook, bishop and queen of modern Western chess, the drunk elephant that promotes to a second king, and also the even more powerful lion, which among other idiosyncrasies has the power to move or capture twice per turn. Around the 14th or 15th centuries, the popularity of dai shogi then waned in favour of the smaller chu shogi, played on a smaller 12×12 board which removed the weakest pieces from dai shogi, similarly to the development of Courier chess in the West. In the meantime, the original 9×9 shogi, now termed sho shogi, continued to be played, but was regarded as less prestigious than chu shogi and dai shogi. Chu shogi was very popular in Japan, and the rook, bishop, and drunk elephant from it were added to sho shogi, where the first two remain today.