Complex sentence: The importance of the Far East Front gave Blyukher a certain degree of immunity from Stalin's purge of Red Army command, which had begun in 1937 with the execution of Mikhail Tukhachevsky--in fact, Blyukher had been a member of the tribunal that convicted Tukhachevsky.
Split into simpler sentences: The importance of the Far East Front gave Blyukher a certain degree of immunity from Stalin's purge of Red Army command, which had begun in 1937 with the execution of Mikhail Tukhachevsky. In fact, Blyukher had been a member of the tribunal that convicted Tukhachevsky.