Complex sentence: A second generation of the missile (AIM-9G/H/J) was introduced during 1970 and these were followed from the mid-seventies by the AIM-9L/P which was a substantial improvement on the early versions particularly with an improved SR-116 reduced-smoke rocket motor.
Split into simpler sentences: A second generation of the missile (AIM-9G/H/J) was introduced during 1970. These were followed from the mid-seventies by the AIM-9L/P which was a substantial improvement on the early versions, particularly with an improved SR-116 reduced-smoke rocket motor.