Complex sentence: Nearly all of the discontinued units were heavy bombardment groups (B-17 and B-24), numbering only 35 at the war's end, the rest inactivated or redesignated as very heavy bombardment (B-29).
Split into simpler sentences: Nearly all of the discontinued units were heavy bombardment groups (B-17 and B-24), which numbered only 35 at the war's end. The remainder had been inactivated or redesignated as very heavy bombardment (B-29).