Shatarnge,(SP?) Chataranke, (SP?) and Byzantine are three forms of early chess. Currently Byzantine is played on a circular board, Both the others are played on a standard 64 square board. (which shows they've been adapted to current standards)
Both the others are played with minor differances in how a couple of the pieces move. I do not recall exactly which goes where, (haven't played em in 30+ years)
but in one, the king can move up to 2 squares on the angle, (involving a jump capture)
The other the bishops only move 2 squares at a time. Also in one of the two, the queen may only move 1 square at a time, except to capture, (the only time she gets full run of a column, row, or angle.
The Ottoman Empire is credited with being the birthplace of modern day chess, brought back by the crusaders, in their many Holy Wars, with credit also going to both Egypt, and the Danes for having quite similar games found in various burial sites. So Chess is the original war game....
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GreyBeard
Flt Ldr
Skeleton Crew