Freelancer Ethan H. Calk sold this story on his very first pitch session to Star Trek: Deep Space Nine. He pitched numerous other ideas before finally landing his second sale - contributing to the story for the episode Children of Time (1997).
In his pitch, Calk had used Nausicaans as the villains, but these were rejected as not familiar enough. In response, he created the Romulan-Klingon intrigue plot.
This episode features the first appearance of the D'deridex-class Romulan warbird in Star Trek: Deep Space Nine.
Bashir uses a familiar-looking tool to adjust the armband that O'Brien uses to shift forward in time. It's a warp nacelle from a Romulan Warbird model. The tool is slightly modified; it's colored gray instead of green, and blinking lights are added on the inside.
Bashir's use of hyronalin as a treatment for radiation poisoning is a reference to The Deadly Years (1967).