If you are directly admitted to the command college in high school, you don't have to. Theoretically, after graduation, you are directly assigned to the troops near your hometown. However, if you are a national defense student, you usually have to go to the command college for one year (depending on your major), which mainly includes physical training, learning how to command, how to do daily management, military guidance law and so on. It usually begins in the summer vacation after graduation from college.