I need you. You are crucial to the success of this crabigator army. Please join us.
The army squad is an army. It's also just the army. It refers more to "an" army rather than "the" army. Just a group of people who do army things.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.