Some of my non-Muslim friends say that Islam, in its early stages, was spread by attacking other nations and by the sword. Is this true? If so, does it not contradict the principle that fighting is only allowed for self defense?
The claim of your non Muslim friend is untrue. He might be influenced by wrong anti Islam propaganda.
Quran is very clear that (No compulsion in religion)(2:256). The Prophet Muhammad (SAWA) never forced any one to become a Muslim inspire of being the head of the state in Madina. Non Muslims lived free in their faith during his government.
We never fight to force people to become Muslims and we believe that I forced faith is invalid. We fight just to defend ourselves, our community and our faith when there an attack on us. Allah says in Quran (And fight in the way of Allah those who fight you but never transgress the limits, surely Allah does not like the transgressors)(2:190).
Muslims ruled over many countries e.g Indian subcontinent, Indonesia, Egypt and African countries but never forced people to b4come Muslims. That is why you find after centuries of Muslim rule, millions of non Muslims are still existing and free in their non Muslim faith. Muslims ruled India for ten centuries and find till today the majority of people there are non Muslims. Those who became Muslims opted themselves by themselves to embrace Islam because of the great teachings of Islam with out any force. Egypt after 1400 years of Muslims rule have till today millions of Copts. Theses are living examples of the freedom of faith in Islam.
Wassalam
