Many have expressed the opinion that those Muslims were motivated by religious zeal to spread Islam by force.
Many other consider this opinion silly and naïve, because Islam – by its nature – cannot be forced.
--Hammudah Abdulati, Islam in Focus, American Trust Publications, London, 1975, p. 146.
Jenkins, Mar 2003
Concepts of Jihad
Differing Opinions on Jihad
Interpretation and Application