The process of assessions is how the Army chooses what component (Active Duty, Reserves, National Guard) and the branch you will commission into. During your MS3 year, you should focus on thinking about what component and branch you would prefer.
Active duty is the most competitive for ROTC commissions. Branching in active duty is based on several assessments of your leadership capabilities such as the Order of Merit List (OML), your Cadet Summer Training Evaluation Report (CER), and your Campus Evaluation Report (CER). Additionally, branching is based on some performance evaluations such as the Talent Assessment Battery (TAB) and branch interviews on HireView.
National Guard and Army Reserve are less competitive. In this component, you will still receive an OML rank and CERs as well as completing the TAB and Branch Interviews, however, your ability to branch into the desired branch is more reliant on your finding a unit that is willing to give you a PL or S Shop position.
Within branches, there is again a range of most competitive to least competitive. This is not meant to discourage you from competing for the most selective branches, although they are harder to achieve they are not uncommon, the Army needs Lieutenants. Aviation, EOD, and Cyber are all competitive branches, requiring extra assessments you must complete in order to be considered. Chemical Corps is always looking for new talent if you're interested.
Branches are also separated into three Tactical Echelons as they relate to combat in executing missions. Some branches fall under multiple Tactical Echelons because they perform a variety of missions. If you'd like to read more check out this webpage.
Air Defense Artillery
Armor
Aviation - Firepower & Cavalry OPNs
Engineers - Combat Engineers
Field Artillery
Infantry
Special Operations Forces*
Aviation - C2 OPNs
Chemical Corps
Engineers - Mobility & Defense Engineers
Military Intelligence
Military Police Corps
Signal Corps
Special Operations Forces - Civil Affairs
Adjutant General Corps
Aviation - Air Movement OPNs
Chaplain Corps
Fiance Corps
Engineers - Civil Engineers
Medical Corps
Ordnance Corps
Quartermaster Corps
Transportation Corps
There are also some options that may help you achieve your desired branch if you are willing to volunteer more years of service. An Active Duty Service Obligation (ADSO) is what every ROTC active duty cadet receives if they are on active duty. However, there is an option to volunteer for an additional ADSO for the benefit of increased probability of receiving your desired branch.
The Branch Detail program allows cadets to choose a basic branch (usually Military Intelligence, Signal, Finance, Air Defense Artillery), but also assigns them to a control branch (Infantry, Armor, Field Artillery, Chemical) – where they will serve immediately the following commissioning (source). Selecting a detail may make you a more competitive candidate for your desired branch.
The graduate school option (GRADSO) has been suspended since 2014. For more information, visit this source.
The talent assessment battery is an online assessment of your skills and competencies. It will rank all of your abilities and be used to match you with the branch that best matches you. See this source.
Branch interviews are a cadet's way to show the branching staff which branches they are interested in and to argue why they are well suited to them. Hirevue is an online interviewing tool that the army uses the execute branch interviews. During the interview, process cadets can access links to each branch's interview through the TAB website. The interviews include written, multiple choice, and recorded response questions. Each branch's interview is unique. Most cadets will interview four to six branches.
Post-Selection Timeline:
Open to all branches except Aviation selected for Active Duty
Volunteering to participate in the program does not guarantee being selected for the Post of Choice program
The Post ADSO (PADSO) option allows cadets to volunteer for a three-year ADSO in exchange for receiving one of two desired first duty stations. PADSOs are not available for cadets branching aviation. If you are not accepted into the PADSO program you will receive your branch through the normal board and will not be expected to serve the 3-year ADSO.