Complex sentence: While he was there, the Israel Defense Forces attacked the city and as a result most of its civilian population was forced to leave, and marched for three days without food or water until they reached the Arab front lines.
Split into simpler sentences: While he was there, the Israel Defense Forces attacked the city and as a result most of its civilian population was forced to leave. They marched for three days without food or water until they reached the Arab armies' front lines.