Kelly Severide (Taylor Kinney) is a tough man to pin down these days. He's always been a proud firefighter, but the older he's gotten, the more intrigued he's become with arson investigation. He clearly has a knack for it, as evidenced by the fact that Wendy Seager (Andy Allo) enlists his help whenever there's a particularly difficult case.
Severide's decision to pursue arson investigation in season 11 is ultimately why he was absent from the last third of the season, but the emphasis on this particular interest can make it confusing when looking at the rest of his career. Severide is, at the end of the day, a firefighter, and his rank within the 51 reflects this.
Severide was the youngest squad member in Chicago history
As of season 12, Kelly Severide is a lieutenant. It's an impressive, rank to be certain, and it makes sense when considering his historic rise within the firehouse, but Severide's career trajectory hasn't always been the smoothest. Let's recap, shall we?
Severide actually made Chicago history as the youngest firefighter to make squad. He was only 23 years old, which meant that he was slapped with the "wunderkind" label. His career was on a steady upward trajectory until season 4, when he ran afoul of the Deputy District Chief Ray Riddle (Fredric Lehne).
Riddle planned to take over as Chicago Fire Commissioner by ousting Chief Boden as Battalion Chief and replacing Severide with the similarly ambitious Captain Dallas Patterson (Brian J. White). Severide was subsequently stripped of his lieutenant rank, which struggled to do his job under Patterson's rule. Thankfully, Riddle was taken care of by the end of the season, and Severide was reinstated.
Kelly Severide has yet to be promoted to Captain
The next step for Severide, of course, would be getting promoted to Captain. It's an honor that was given to his best friend, Matthew Casey (Jesse Spencer), in Chicago Fire season 6, but it has escaped Severide for over half a decade.
While it makes sense on a certain level (Matthew Casey has always been the by-the-book firefighter of the two), it is hard to overlook the fact that Severide is one of the most fearless and consistenly praised firefighters on the show.
The belief that some fans have is that the writers are waiting to bestow the rank of Captain to Severide until the end of the show OR the end of his run on the show. Only time will tell if this prediction turns out to be true.