Complex sentence: Only 833 F-105 Thunderchiefs had been built, and having lost nearly 50% of that production figure in Vietnam, the F-105 was by military standards almost no longer combat-effective.
Split into simpler sentences: Only 833 F-105 Thunderchiefs had been built. Having lost nearly 50% of that production figure in Vietnam, the F-105 was by military standards almost no longer combat-effective.