That I never sang in the church
And I took one night for the town to decide
I'm afflicted by the curse
Unreligious people were usually doomed as witches since they didn't listen God's word and probably worshiped some other god's - aka. Satan for Church. Also people who broke rules or just had a good luck were usually blamed for using dark magic.
In middle ages, those who were judged as a witches could only prove their innocence by dying in a test which a witch would survive. So even after proven themselves innocent, they couldn't get the justice they deserved.
Mostly just telling how people around soldiers will eventually all just die in battles, leaving them standing alone. And eventually making them lost their way to make friends - since they're all just going to die anyway.
Since black is colour usually wore at funerals and colour for mourning and sadness, this practically means that even the God already knows the men are going to die and never come back; treating their leaving as a funeral.