raise
raise, you mobilize the army.
Raise.
Mount
conscript
Ditto. (Swear to Og, I didn’t look at your answer first - it was just the first word that popped into my head. GMTA?)
2 votes.
Yes!
“Amass” was the first word that came to mind.
Another vote for “raise”.
The first part of the sentence isn’t very grammatical either. You should probably say “Faced with a growing threat, the new government decided to RAISE an army.”
Just saying…
…and another for “raise.”
My boyfriend made a reference to constructing an army during a chat a few weeks ago, and I laughed, because I was picturing him making soldiers out of two-by-fours.
And then we got into a very silly but very heated debate about which word was appropriate to use when talking about starting up/recruiting/raising a new army.
Since he won’t give up, I figured I’d poll total strangers (to him, anyway) and see whether “construct” came up.
And it didn’t.
Does that mean I win?
Yes.
Construct an army? There probably aren’t 3 people in the world who would say that.
tickle?
I don’t like to fight! Don’t raise me!
Actually, I thought of “train” then “draft.”
Construct would never have been on my list.
engorge 
“Facing a growing threat, the new government decided to _______ an army.”
hide behind
Obliterate came to mind first, followed by conscript.
Why, yes, I’ve been playing a lot of Risk lately. Why do you ask?
The first word that came to mind is “raise,” because I’m a citizen of the United States, in which we do that sort of thing. I, for one, am glad that I’m out of the “raising” age limit, which indicates that at least my second word is “draft.”