Botvinnik was a fighting world champion who defended the title frequently. He would hold the title from 1948 until 1963 with only two brief interruptions where he lost the title but would quickly regain it in a rematch. His first title defense came in 1951 match against David Bronstein. The two played to a 12 to 12 draw and Botvinnik retained his title. In 1954 he once again drew 12 to 12 to retain his title, this time against Vassily Smyslov . In 1957 Smyslov would take his revenge and defeat Botvinnik 12 ½ to 7 ½ becoming the seventh world chess champion. Botvinnik evoked his rematch clause and defeated Smyslov the following year. In 1960, Botvinnik would once again lose his title to the brilliant young talent, Mikhail Tal by a score of 12 ½ to 8 ½. Botvinnik once again took lessons from his defeat and would redeem himself and defeat an ailing Tal the following year in their rematch. Botvinnik would lose the title for good in 1963 vs. Tigran Petrosian. A change in FIDE rules no longer allowed a champion to automatically qualify for a rematch.
Botvinnik was not only a prolific world chess champion but is considered the father of Soviet Chess. He was arguably the games strongest player for a span of 30 years. His long tenure at the top and his mentoring of younger talent helped make the Soviet Union the dominant nation in chess throughout nearly all of the Cold War. With state sponsorship he founded the famous "Botvinnik School" that would find the brightest young talent in the USSR and groom and train them into future world champions. The Botvinik School indeed produced several world champions including: Anatoly Karpov, Gary Kasparov and Vladimir Kramnik. Botvinnik was one of the first to realize the importance of preparation including physical fitness. He was also one of the first to experiment with computer chess. Botvinnik passed away on May 5th, 1985. His contributions to chess are countless. He was without a doubt one of the greatest world champions that ever lived.
Some Quotes on Botvinnik:
"Chess is the art of analysis."
"Chess is art that expresses the science of logic."
"There is no better place for learning to work independently and to extend your horizon than higher school."
"All told, there is not a single weakness in his armor." – Rueben Fine
"My studies with Botvinnik brought me immense benefit, particularly homework assignments which forced me to refer to chess books and work independently." – Anatoly Karpov