The two younger Russians clearly regard Rilke as a luminary and model for the ambitious Modernist lyric-poetry they were engaged upon: "For Tsvetayeva and Pasternak, Rilke's poetry was the highest proof that in this divided and distorted world there exist real and immutable values not to be measured by pragmatic standards" (Introduction). Tsvetayeva in one letter calls him "poetry incarnate". For his part, Russia had always held a totemic significance for Rilke: he travelled there as a young man, met Tolstoy and developed a huge reverence for the earthy humility of peasant life - he even attributed his experience of Russia as the starting-point of his mature poetry, that grasping of the centralness of "thingly utterance" ("sachliche Sage"), of the numinous within the quotidian, he always adhered to.
The correspondence between Rilke and the Russian poets was in fact initiated by Pasternak's father, the composer Leonid, a friend from Rilke's Russian days - we recall the tantalizing childhood-memory at the beginning of Safe Conduct (Pasternak's superb set of autobiographical sketches, dedicated to Rilke) of seeing off on a train a vaguely-recalled German-speaking figure. Ultimately one feels a little sorry for Boris: he writes one reverential letter to Rilke on the back of his father's, in which he quite selflessly makes an epistolary introduction to Marina Tsvetayeva ie. can she write to you? Rilke replies to Pasternak, giving him his blessing as a poet - Boris is so over-awed he keeps the letter in his breast-pocket for the rest of his life. But Marina then rather takes over the correspondence and makes it her own, showering Rilke with compliments and breathless superlatives, while Boris - from diffidence and tact, knowing that the older man is unwell - holds back and in fact never actually writes to Rilke again.
Rilke is obviously flattered by Marina's rapturous hyperboles and even writes her a poem - 'Elegy for Marina' - which Tsvetayeva later calls "the last Duino Elegy" though it hardly matches up to the quality of the already-completed cycle. The degree to which - in their far-flung poetic prose - Rilke and Tsvetayeva seem to be flirting with each other in their letters is interesting to consider - certainly the photographs of himself Rilke sends her show him in some oddly coy or kittenish poses (were spats ever deemed attractive, one wonders!) Ironically, in her final letter to him, it seems that Marina might be trying to suggest an assignation ("Dear one, when at some point you really want to, you write to me - a little beforehand, for I have to find somebody to stay with the children - and I'll come") without knowing that Rilke was by then in the terminal stages of cancer. He died on December 29th of the same year.