Ever since 1993, when Garry Kasparov and Nigel Short broke away from chess governing body FIDE to play their world championship match under the auspices of the newly formed Professional Chess Association, there had been two chess world championships: one organised by FIDE (which used the knock-out format from 1998 to 2004) and one by a variety of other bodies (in the form of a long match between champion and challenger). The 2004 FIDE Championship was a part of what was, at the time, the most serious attempt yet to reunify the title, the so-called "Prague Agreement".