Complex sentence: He was able to achieve great success, capturing the important Iranian city of Khorramshahr, although the Iraqis where not able to capture the city of Abadan the way was open to Tehran as the Iranian defences had collapsed.
Split into simpler sentences: He was able to achieve success, capturing the important Iranian city of Khorramshahr. Although the Iraqis where not able to capture the city of Abadan, the way was open to Tehran as the Iranian defences had collapsed.