Dear Br. A. As-salaamu alaykum. Islamic Law doesn't preach the killing of non-believers (or the infidels) indiscriminately. Killing and wars are the exceptions and not the norm. Muslims are to live harmoniously and to deal justly with non-Muslims. This is confirmed in Surah al-Mumtahinah (60) verse 8. It is also very well documented in Islamic History that Prophet Muhammad (pbuh) sent ambassadors to the non-Muslims to invite them to Islam. The permission to go into wars have strict codes and rules. Thank you for asking and God knows best.
(Source: IslamiCity) Classified in Killing and Wars >