Complex sentence: Louis'championship reign lasted 140 consecutive months, during which he participated in 26 championship fights; a 27th fight, against Ezzard Charles in 1950, was a challenge for Charles' heavyweight title and so is not included in Louis' reign.
Split into simpler sentences: Louis'championship reign lasted 140 consecutive months, during which he participated in 26 championship fights. The 27th fight, against Ezzard Charles in 1950, was a challenge for Charles' heavyweight title and so is not included in Louis' reign.