What were the soldiers that fought for Islam called?

Answer 1

Mujahidin. One soldier would be a mujahid. The word is formed from "jihad," literally "struggle" but generally used to mean "holy war." The prefix "mu-" serves the same grammatical function as the English suffix "-er," that is, to identify a participant. In Arabic, there is a vowel mutation when the "mu-" is added, thus "jihad" -- "mujahid"; "Islam" -- "Muslim."

A note on the Arabic grammar - the "mu" is not a prefix, it is part of the Arabic "fa3el" paradigm (which has prefixes and infixes) also creating vowel changes. It just happens that in these cases, it becomes the "-er" suffix in English.

Answer 2

A Muslim soldier may be called by different names in different languages. In Arabic he is called Mujahid - a person who strives in the path of Allah Karim. In a way, the whole life of a true Muslim is spent, or should be spent, in the way of Almighty God. Earning livelyhood by lawful means, rearing and educating his family and children, helping the poor and the needy, serving human beings, retraining himself from doing injustice to others and acts like these are all Jihad.