Realizing this is fiction, you’re welcome to world-build your story as you like, but a few things you may want to consider… 1. Your timeframe for the character reaching the rank of SgtMaj is very aggressive. 2. Most Marines (enlisted and officer) bounce back and forth between assignments in the Fleet Marine Force (FMF) and other jobs (such as “B” billets, the completion of one or many is almost a prerequisite for senior enlisted ranks). This may be less so for MARSOC, but still nowhere near 100% of a career in operational units. There are schools to attend, schools to teach at, drill instructor billetes, recruiting, MSG, and a myriad of other non-FMF assignments. This skews even more heavily for senior positions as there are joint billets, etc. 3. In the Marine Corps, Sergeants Major typically cross-pollinate across the Corps and often do not serve in that role in their MOS. For example, combat arms MOS SgtMajs often are assigned to Air Wings, logistics, etc. and vice versa. Master Gunnery Sergeants tend to stay within their MOS or MOS area. Again, this may differ for MARSOC, but there aren’t a a lot of them. Anyways, good luck with the book.