Like many Star Trek: Deep Space Nine characters, Major Kira Nerys (Nana Visitor) underwent a complex character evolution throughout DS9‘s seven seasons. Star Trek: Deep Space Nine‘s First Officer was originally supposed to be Star Trek: The Next Generation‘s Ensign Ro Laren (Michelle Forbes), but when Forbes declined to return as Ensign Ro, DS9 created Major Kira instead. Unlike Ro Laren’s Starfleet-adjacent point of view in TNG, Kira’s backstory in the Bajoran Resistance placed her closer to the front lines of the conflict between the Bajorans and their Cardassian oppressors.

https://screenrant.com/star-trek-ds9-kira-complete-timeline/