I want to know the answer to the following question:
Who became speakers of Balto-Slavic?
All the background I'm provided with is that "Proto-Slavic, the supposed ancestor language of all Slavic languages, is a descendant of common Proto-Indo-European, via a Balto-Slavic stage in which it developed numerous lexical and morphophonological isoglosses with the Baltic languages.". Is that enough to answer the question?
Answer: no