NDA is a training academy for defence forces. Cadets who get selected after NDA exam and SSB interview, a merit list is prepared for all three departments Army, Navy, Air force. The cadets gets training in the academy for 3 years. After that they are sent for 1 year training to concerned Academy for army in IMA, for Navy in INA, For Air force in AFA. After 1 year training in their concerned academy they get commissioned as officers. So total period is 3 yrs NDA and 1 year at concerned Academy. NDA do not recuit directly to any force, it gives training to the cadets and mould them into officers. Nothing like Higher post and all. The cadets get commissioned after 4 years, they will get promotion as per the procedures and also they have to undergo various steps for promotion. You no higher post as such, till your retirement which post you can achieve is highest. Seniority is also a criteria.