Breakdown of Понимая опасность, он не мог не вмешаться и не рискнуть.
и
and
не
not
он
he / it (for a masculine noun) / it (for a neuter noun)
понимать
to understand
Questions & Answers about Понимая опасность, он не мог не вмешаться и не рискнуть.
How does the double negative не мог не вмешаться translate to "couldn't help but intervene"?
In Russian, using не with a conjugated form of мочь (like мог) followed by another не and an infinitive creates a strong affirmation. Literally, it means "he could not not intervene," which translates naturally to "he couldn't help but intervene" or "he had to intervene."
Why is не repeated before the second verb, рискнуть?
The second не is required to keep the double negation going for the second action. Without it, the sentence would lose the "couldn't help but" meaning for the second verb, breaking the parallel structure. To say he couldn't help but do both things, you must place не before each infinitive.
Why is the verbal adverb понимая imperfective, while the main verbs вмешаться and рискнуть are perfective?
Понимая (understanding) is imperfective because it describes an ongoing background state happening at the exact same time as the main actions. The main verbs вмешаться (to intervene) and рискнуть (to take a risk) are perfective because they are specific, completed actions he took as a result of that understanding.
What case is опасность in here, and why does it look like a dictionary form?