The most effective, the most deadly, the most terrifying weapon of all time was. Yes, you're right. The sergeant's whistle.
11 seconds sound clip from the At War with the Army (1950) movie soundboard.
You can hear this line at 00:02:42 in the DVD version of the movie.
Quote context
[...]
- Was it the withering stutter of the light machine-gun? Or the spectacle from the commanding troops?
- Or is it the prival juggernaut the Patton tank?
- Or was it the screaming anger of faster than sound, quicker than this: B-2 rocket?
- No! It was none of these things.
- All right you guys, now I'm gonna tell you something.
- Well, the Colonel is coming, see? And as usual the Colonel ain't very happy.
- And I ain't very happy either.
- Look at this joint. It looks like Coney Island on a Monday morning.
- Hi Sarge, what's the action?
[...]