I have only heard of "The Autumn Order of the Soldiers on the Battlefield", which comes from "Breaking the Array: Writing Poems for Chen Tongfu". The whole poem is as follows:
Xin Qiji
When I was drunk, I lit up the lamp and read the sword, and I dreamed of blowing the trumpet in the camp.
Eight hundred miles away, the soldiers under the command are burning, the sound of fifty-stringed strings turning outside the Great Wall, and the autumn order of troops on the battlefield.
The horse is flying fast, and the bow is like a thunderbolt.
Finish the affairs of the king and the world, and win fame during and after life. Misfortune happens in vain!
I specifically checked some information, but could not find any poems related to the autumn troops on the battlefield outside the pass. I suspect you remembered it wrong. I hope you will think about it again.