Praise be to Allaah.
Islam was spread by proof and evidence, in the case of those who listened to the message and responded to it. And it was spread by strength and the sword in the case of those who stubbornly resisted, until they had no choice and had to submit to the new reality.
And Allaah is the source of strength. May Allaah bless our Prophet Muhammad and his family and companions, and grant them peace.