This is not talking about waging war on nonbelievers it is about the people of that time to defend themselves and stand strong against those who attacked them,killed their families, displaced them from their homeland ,and also who tries to stop them from worshipping their God. Islam is the religion of peace guys you have to be open-minded and study deeply. it is known that in Islam if you kill one soul weather a believer or not it will be as though you have murdered the entire world population.