Complex sentence: The number of refugees that has escaped through Portugal during the war has estimates that range from one hundred thousand to one million, an impressive number considering the size of the country's population at that time (circa 6 million).
Split into simpler sentences: The number of refugees that has escaped through Portugal during the war has estimates that range from one hundred thousand to one million. An impressive number considering the size of the country's population at that time (circa 6 million).