Pacific Chess was described late 1971/early 1972 by John Mantle Green, wro wrote to John Gollon (author of Chess Variants: Ancient, Regional, and Modern). Gollon send parts of a draft of a followup of his book to Eric Greenwood in 1976; Eric communicated this information to me in 1997.
Pacific Chess was played in Hawaii. As Green did not know the original name of the game, he named it Pacific Chess because of where he saw the game played. He thought that the game was probably a local experiment that players found interesting.
A related game is Mideast Chess. (Green stated that some players had moved from California, the origin of Mideast Chess to Hawaii.)
Pacific chess is played by two players on a ten by ten board. Each player has in addition to a normal set of pieces, two castles, two fortresses, two guards, two noblemans, and two extra pawns.
The starting setup is as follows:
King f2; Queen e2; Rook a2, j2; Knight b2, i2; Nobleman c2, h2; Bishop d2, g2; Castle a1; j1; Fortress c1, h1; Guard e1, f1; Pawn a3, b3, c3, d3, e3, f3, g3, h3, i3, j3.
King f9; Queen e9; Rook a9, j9; Knight b9, i9; Nobleman c9, h9; Bishop d9, g9; Castle a10; j10; Fortress c10, h10; Guard e10, f10; Pawn a8, b8, c8, d8, e8, f8, g8, h8, i8, j8.
The king, rook, knight, bishop, and pawn move as in orthodox chess, but pawns can also promote (when they reach the last row) to castle, fortress, guard, or nobleman, as well as to queen, rook, knight, or bishop. There is no castling.
The queen has the combined moves of queen and knight.
The nobleman moves as a queen from usual chess.
The castle moves as a knight, or can jump to any square that is horizontally, vertically, or diagonally two squares away. So, a castle on d4 can jump to b2, b3, b4, b5, b6, c2, c6, d2, d6, e2, e6, f2, f3, f4, f5, or f6.
The fortress moves one square diagonally, or jumps two squares horizontally or vertically.
The guard moves one square in an arbitrary direction (i.e., as a king, but it may moved to an attacked square, etc.)
Other rules are as in orthodox chess.
Gollon suggested to allow pawns to make an initial triple step, extending the en passant rule to all squares passed by by the pawn. Also, Gollon suggested to allow castling, where the king always moves three squares when castling; other castling rules as in orthodox chess.