Since the idea of making submarines sparkled in human’s mind, it was also an interest how it could be kept under water for a longer period of time. After the importance and the strengths of submarines were proved in World War II, all efforts in the sub-marine industry was directed to find a solution for the most fundamental problem with submrines; that is, a need to come to the surface in order for the batteries to get recharged. The creation of air-independent propulsion system was but a revolution in naval instruments, not less important than the first revolution- the very making of submarines. While many countries like Britain, the USA, and the former Soviet Union during their research and experiments, and with the development of nuclear energy for propulsion, many other industrial and developing nations which did have a naval force, but could not take benefit of nuclear energy, managed to increase the endurance time using air-independent propulsion system in conventional sub-marines. The paper aims to investigate the creation and development of AIP in non-nuclear sub-marines, and attention to the significance of this revolution in sea operations (sub-marinal and anti-submarinal).