The word "army" here could refer to a literal army, or it could be a metaphor for an organized group. (See: [[rc://en/ta/man/translate/figs-metaphor]])
This could be translated as "They were praising God."
## Glory to God in the highest ##
Possible meanings are 1) "Give glory to God in the highest place" or 2) "Give the highest glory to God." It could be translated as "speak of God's glory in the highest place" or "Give God the highest praise."
## may there be peace on earth among people with whom he is pleased ##
"may those people on earth with whom God is pleased have peace"