Learn Russian: Пророчество уже сбывается — нам не предотвратить эту битву. - The prophecy is already coming true

This sentence uses an independent infinitive clause to express impossibility, which is the focus of your current lesson. By using the dative subject нам (to us) plus не and the perfective infinitive предотвратить (to prevent), it creates a fatalistic feeling. It implies that it is beyond our power or destiny to prevent the battle, which sounds much stronger and more literary than a simple мы не можем (we cannot).

Why use the perfective verb предотвратить after не? Don't we usually use the imperfective for negative actions?

While standard negative commands and regular statements often use the imperfective aspect to show an action shouldn't happen at all, this specific dative-infinitive construction has its own rules. When you use не plus a perfective infinitive in this structure, it specifically means that a successful result is impossible to achieve. It translates as a helpless "we will not manage to do it."

How does the verb сбывается work here? Is it a passive form?

Yes, the -ся ending acts to make the verb intransitive or passive here. The verb сбываться (imperfective) or сбыться (perfective) is a dedicated vocabulary word used almost exclusively when talking about dreams, predictions, or prophecies realizing themselves or coming true. We use the imperfective сбывается here because the prophecy is actively in the process of coming true right now.

Why is in the accusative case here instead of the genitive? Doesn't negation sometimes require the genitive case?