Complex sentence: A large number of early MiG-21 variants were withdrawn from service and were cut for scrap, and armament from the trainers for the MiG-21 and MiG-23 was removed.
Split into simpler sentences: A large number of early MiG-21 variants were withdrawn from service and were cut for scrap. And the armament from the trainers for the MiG-21 and MiG-23 was removed.