The Alexandrian Ring

Description for THE ALEXANDRIAN RING by William R Forstchen:

First there was war, then there were wargames, growing more and more realistic until the games themselves surpassed war as mankind's most popular sport. But with no blood, guts, or glory, boredom began to set in and strategy lost its edge. Something was needed to bring fresh excitement to an old, old game. And so the past was mined for the greatest warriors and generals history had to offer: Napoleon, Alexander, the 47 Ronin, assassins from ancient Persia—all brilliant at either combat or at tactics and strategy.
It was just a game—until mock war turned real on an unimaginable scale, and only those legendary warriors could turn the tide.

This is #1 in Gamester Wars.