What happens in a sit-in and it's consequences

It's a form of direct protest in which a group want to encourage social or political change. Groups often refuse to move from the place in which they are protesting until they see a significant change. SNCC, for example, organised many restaurant counter sit-ins in the 1960s. This was to protest against racial segregation and discrimination. Many people reacted negatively to the sit-ins movement during this time, but the majority of protesters continued to use peaceful protest methods so that they didn't sacrifice their morals and could attract media attention.

They weaken the south vietnamese army.