Breakdown of Он должен был совершить этот подвиг ради неё.
он
he / it (for a masculine noun) / it (for a neuter noun)
она
she / it (for a feminine noun)
этот
this [f: эта, n: это]
быть
to be
Questions & Answers about Он должен был совершить этот подвиг ради неё.
Could we just use для неё instead of ради неё here?
You could, but the meaning shifts slightly. для is the general preposition for "for" (as a benefit or intended recipient). ради, however, means "for the sake of" or "in the name of." It implies a higher purpose, sacrifice, or strong dedication. Given that he is performing a подвиг (heroic deed), ради elevates the sentence to match that dramatic tone. Both take the Genitive case.
I know ради takes the Genitive case, but why is it неё instead of её?
When third-person pronouns (он, она, оно, они) immediately follow a preposition that governs their case, Russian adds an н- to the beginning of the pronoun to make it easier to pronounce. So, the normal Genitive её becomes неё after the preposition ради.
Why use совершить instead of a common verb like сделать?
совершить means "to accomplish," "to perform," or "to commit." It is highly formal and used for significant, weighty actions, both good and bad. It naturally pairs with words like подвиг (a heroic deed), преступление (a crime), or открытие (a discovery). Using сделать here would sound far too casual and mundane for a heroic feat.
How does the grammar of work to mean "he had to"?