Yes, longitudinal waves need a medium to continue moving forward.

Which is a longitudinal wave that requires a medium to move?

An example of a longitudinal wave that requires a medium to move is sound. Sound is a mechanical wave, which means it needs a medium to propagate. …

Which waves require medium and which does not?

Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.