Linked from
The 15 pages that link to Warsaw Pact invasion of Czechoslovakia, each with the reason it gives.
Prague SpringBroader topic: The invasion forcibly halted the reform movement.
AlbaniaRelated: Albania condemned the invasion and used it to justify formally leaving the pact.
Brezhnev DoctrineBroader topic: The invasion became the action the doctrine was used to defend.
Jan PalachRelated: The invasion began the occupation against which Palach later protested.