In perhaps his most famous work, the essay "Power of the Powerless", Havel explained why.
"You do not become a "dissident" just because you decide one day to take up this most unusual career. You are thrown into it by your personal sense of responsibility, combined with a complex set of external circumstances," he wrote in 1978. "You are cast out of the existing structures and placed in a position of conflict with them. It begins as an attempt to do your work well, and ends with being branded an enemy of society."
Havel's contemporaries said he played a big role in underground newspaper "tvar", which set off the dissident movement in the 1960s, but not only because of his literary prowess.
"He was the only one among us who owned a car, which obviously helped a lot," said fellow dissident Bohumil Dolezal.
In 1976, there was a crackdown on the rock group The Plastic People. That triggered the Charter 77 movement, which criticised the government for failing to uphold human rights.
Havel's wife Olga began organizing gatherings at their weekend house north of Prague, where bands played in the barn, and police erected an observation point in a neighbouring plot.
According to Dolezal, he and Havel parted ways after 1968 because of diverging of views, but they met again in October 1988, when they had both been arrested and held for four days.
"There we were," he said. "Everything confiscated from us, including shoe laces, so that we would not commit suicide, and we talked about politics, which we probably otherwise would not have had a chance to do."
EAGER ROCKER, RELUCTANT LEADER
Friend and fellow Charter 77 member Petruska Sustrova recalled how Havell usually had the last word on what they published but refused to acknowledge his influence. That unassuming nature came to the fore when it became clear he would be president.