You can find this information anywhere and everywhere. The fact that this simple fact escapes you means you are either extremely lazy and not even doing the most basic research into what you're saying, or you're taking your information from the dark web and other random overnight sources that aren't remotely legitimate.
Here's one link i just found randomly. I suggest you catch up on your reading instead of relying on what the old guy down the street told you.
Republican vice presidential nominee and Ohio Sen. JD Vance sought to negatively frame the 24-year military career of Democratic vice presidential candidate Tim Walz, Minnesota’s current governor.
www.pbs.org
"Although Walz had been promoted in 2004 to command sergeant major, he retired in 2005 as a master sergeant, one rank below command sergeant major, “for benefit purposes because he did not complete additional coursework at the U.S. Army Sergeants Major Academy,” Augé said."