Difference between prepositions in "...killed during/in the war"

I'm studying prepositions. In this part of speech, I'm confused between the use of 'in' and 'during':

1. Rani Laxmi Bai was killed during the war. (❌)

2. Rani Laxmi Bai was killed in the war. (✔)

How is the first one incorrect?

In some contexts in and during are interchangeable. But here, as Jason Bassford points out, in means more than just "during the time of": it implies that her death was in some way because of the war - she was fighting, or she was bombed, or perhaps she was executed as a spy.

During would here mean just "during the time of the war", and choosing it rather than in would imply, as Jason says, that her death was not connected with the war.