What is the meaning of an army in the Bible?

Answer 1

Exactly the same as it means today. Essentially as organized group of people ready to fight for a nation or a cause. Although the weapons were different in technology, and the Geneva convention did not yet exist, the basic intentions of an army at war have not changed in history.

Jesus referred to 'legions of angels' (a reference to the Roman army organization of His day) as hosts of heavenly beings ready to defend Him if called upon. He did this to make a certain point, although on a number of other occasions spiritual warfare is recorded or alluded to in scripture. This is between heavenly beings, angels versus demons, or in terms of Christians resisting the devil's attacks. Although in the latter case this is on the individual level.