Complex sentence: The International Harvester S-Series was a medium-duty truck line made by International Harvester, started in mid 1977, introduced as a replacement for the International Harvester Fleetstar.
Split into simpler sentences: The International Harvester S-Series was a medium-duty truck line manufactured by International Harvester. The S-Series was first introduced in mid- 1977 as a replacement for the International Harvester Fleetstar.