Complex sentence: In the absence of any other air power, the Raven FAC fired a marking rocket at one of a pair of PT-76 tanks; the sonic boom of the rocket frightened the Pathet Lao infantry into retreat.
Split into simpler sentences: In the absence of any other air power, the Raven FAC fired a marking rocket at one of a pair of PT-76 tanks. The sonic boom of the rocket frightened the Pathet Lao infantry into retreat.