Complex sentence: LRRP rations were designed to be lightweight and easily portable, a precursor of the U.S. military's current Meal, Ready-to-Eat (MRE) field ration.
Split into simpler sentences: LRRP rations were designed to be lightweight and easily portable. The LRRP ration was a precursor of the U.S. military's current Meal, Ready-to-Eat (MRE) field ration.