This is the 656th most frequent Polish word.
wojnie
"Wojnie" means "war" in the dative or locative case in Polish.
Here, 'wojnie' is used to describe a time period of war, specifically meaning 'during the war' in a locative case of specifying the condition connected to the noun 'wojna' (war).
W czasie wojnie wiele osób straciło swoje domy.
During the war, many people lost their homes.
'Wojnie' in this sentence refers to reminiscing about the event of war, used in the locative form of 'wojna'.
Moja babcia często wspominała o wojnie jako o trudnym czasie.
My grandmother often talked about the war as a difficult time.
The word 'wojnie' is applied here figuratively to imply an atmosphere dominated by war; it remains in the locative case.