Those candidates who passed the interview then have to go through rigorous fitness, medical and psychological evaluations. Once the candidate clears these evaluations, the ISI performs a very thorough background check on the candidate before being offered to join the ISI. Security clearance is granted once the candidate accepts the offer. Recruited agents then go to the Inter-Services Intelligence School for basic training following which they are employed on an initial one year probationary period. However, civilian operatives are not allowed to rise above the equivalent of the rank of Major and are mostly assigned to JIX, JIB and JCIB departments and the rest of the departments are solely headed by the armed forces but there have been rare cases in which civilians have been assigned to those departments.
For the armed forces, officers have to apply for admission into the Inter-Services Intelligence School. After finishing the intelligence course, they can apply to be posted in Field Intelligence Units or in the directorate of Military/Air/Naval intelligence. Then they wait and hope that their performance is good enough to be invited to the ISI for a temporary posting. Based on their performance in the military and the temporary posting with ISI, they are then offered a more permanent position.
Senior ISI officers with ranks of Major and above are assigned to the ISI for no more than only two to three years to curtail the attempt to abuse their power. Almost all of the Director-Generals of the ISI have never served in the organization before being appointed by the military commanders to lead it. ISI also monitors former, current and retired military officers who at one point or another held sensitive positions and had access to classified data. However in some special circumstances officers with outstanding achievements are given an extended appointment and even a lifetime (till 60 years of age) job.