Short answers, pulled from the story.
Philip Johan von Strahlenberg published a proposal grouping Turkic, Mongolic, and Tungusic languages together in 1730. He was a Swedish officer who had traveled across the eastern Russian Empire while held as a prisoner of war after the Great Northern War.
Linguists began challenging the genetic connection between Turkic, Mongolic, and Tungusic languages starting in the late 1950s. Gerard Clauson published his case against the theory in 1956 followed by Gerhard Doerfer and Alexander Shcherbak in 1963.
The Orkhon inscriptions dating from 720 to 735 AD are the earliest known texts in a Turkic language. Danish linguist Vilhelm Thomsen deciphered them in 1893 during a scholarly race with Wilhelm Radloff.
Roy Andrew Miller published Japanese and the Other Altaic Languages in 1971 convincing most Altaicists that Japanese belonged within the group. Martine Robbeets proposed in 2017 that Japanese originated as a hybrid language resulting from fusion between proto-Altaic speakers and an agricultural community speaking an Austronesian-like language.
Sergei Starostin published a comparative lexical analysis of Altaic languages in 1991 claiming about 15 to 20 percent shared cognates within a Swadesh-Yakhontov list. The Etymological Dictionary by Starostin, Dybo, and Mudrak included 2,800 proposed cognate sets plus phonological arguments in 2003.