Short answers, pulled from the story.
Linear B was deciphered in 1952 by English architect and self-taught linguist Michael Ventris, building on research by American classicist Alice Kober. Ventris made his first public announcement on the 1st of July 1952 on BBC Radio, describing the language as a difficult and archaic Greek five hundred years older than Homer.
Linear B represents Mycenaean Greek, the earliest attested form of the Greek language. The script predates the Greek alphabet by several centuries, with the oldest known examples dating to around 1450 BC.
Linear B tablets have been found mainly in palace archives at Knossos, Pylos, Thebes, Mycenae, and several other sites across Crete and mainland Greece. Knossos has yielded roughly 4,158 tablets; Pylos around 1,026. The total number of known inscriptions is approximately 6,058.
Linear B tablets were used almost entirely for administrative purposes, recording disbursements of goods such as wool, sheep, grain, and oil at Mycenaean palatial sites. Some tablets deal with military matters. Researchers have identified only 45 individual scribes at Pylos and 66 at Knossos, based on handwriting analysis.
Alice Kober identified that Linear B represented an inflected language with at least three grammatical cases, and she linked signs that shared vowels or consonants without knowing the underlying sounds. She also showed that the word for total changed by gender, pointing toward an Indo-European structure. Michael Ventris built his successful decipherment directly on her classification tables.
Linear B disappeared with the fall of Mycenaean civilization during the Late Bronze Age collapse, around the end of the 13th century BC. The script was confined to palace administration, and once those palaces were destroyed, the scribal community that maintained it ceased to exist. The period that followed, known as the Greek Dark Ages, left no evidence of writing.