This is the 4478th most frequent Russian word.
вплоть
"Up to" or "as far as."
Here, 'вплоть' is used to express the exact endpoint in time, emphasizing the limit reached by the action in question.
Я работал над проектом вплоть до полуночи.
I worked on the project until midnight.
In this context, 'вплоть' underscores the continuation of the hope held by people up to a definitive moment.
Вплоть до окончания войны люди надеялись на мир.
Until the end of the war, people hoped for peace.
'Вплоть' here denotes thoroughness or completeness, ensuring there is no omission even to the smallest unit.