Yeah, to sum it in my view, the Romanovs are rescued from Yekaterinburg by the attempt to do so that never occurred ITTL, with help from the Germans since they're the winners in GW1 and in a better position to do so. They'd very likely foil the plot to kill Michael in nearby Perm, as his wife Natalia Brasova and son George actually had been rescued with German assistance after the fact. Tsar Nicholas would've died a natural death sometime in the early 1930s, leaving the throne to his brother Michael as his son Alexis would have died as a result of his hemophilia, as Turtledove would like to imply in a case of "show and don't tell". After Michael's own death ITTL, the throne would not've gone to his son George as Natalia was of minor rank; thus, the title of Tsar would instead go to his nephew Vladimir Kirillovich, ruling until he dies or is overthrown. Another interpretation that is offered by David bar Elias is that Michael is succeeded by his ATL son who rules as Alexander IV, who probably exists because he either divorced Natalia and married a woman of acceptable rank, or he chooses another woman over Natalia ITTL.
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And indeed, congrats to all here making it to 300 pages! 🥳 🎉 🎊