Blocking smashes is among the most important defensive skills in badminton. If you can't return your opponent's smashes, then your chances of winning the game is slim.
In the NBA, there is a famous saying: Good defense equals good offense. This also applies to badminton. Everybody knows that the smash is an important offensive move in badminton. Smashes, especially jump smashes, are extremely fast and powerful and it is the main attraction for audiences watching a competition. Players and coaches spent years trying to perfect smashes and also smash blocking techniques. In the 80s, there was a famous match where Han Jian from China stopped around a dozen continuous attacks from Liem Swie King of Indonesia, one of the best offensive players in the world at the time, and went on the win the match. There are many other examples of great defense in high level competitions, and all of us recreational players wish that we had that level of defensive skill, so that winning a game becomes easier.
The goal of smash blocking is to prevent the opponents from scoring points from their smashes, and also try to turn the tide of battle. There are many specific smash blocking techniques, but all of them fit into three general categories.