Kira Nerys was born in Dakhur province, Bajor, during the 50-year Cardassian occupation of the planet. After the deaths of her father Kira Taban and her mother Kira Meru, Nerys was recruited to the Shakaar resistance cell, an underground resistance movement which carried out terrorist attacks against Cardassians, both military and civilian.
After Cardassia withdrew from Bajor, Major Kira became an influential figure in its reconstruction and the politics of the region, due to her assignment (then holding the rank of major) to Deep Space Nine, and her closeness to Captain Benjamin Sisko, whom the Bajorans believe to be a spiritual emissary from the Bajoran Prophets.
Major Kira had a relationship with Vedek Bareil Antos until his death in a shuttle accident. She later had a brief romantic liaison with her former cell commander, later first minister of Bajor, Shakaar Edon. During this time, she also agreed to gestate the baby of Miles and Keiko O'Brien, when Keiko was wounded and nearly miscarried during an away mission. She gave birth to their son Kirayoshi in 2373. After she and Shakaar broke up, she started a relationship with with Odo during the Dominion War
She was promoted to Colonel in 2374 during Captain Sisko's personal leave. In that year she proved instrumental in ending the Dominion War, and later took command of DS9 after the disappearance of Sisko at the end of the war.