The Black Legion fought off the attack by the Montenegrin Chetniks of Pavle Đurišić and Tito's Partisans. The name refers to the time between the dawn and full daylight when the Black Legion (Crna Legija) surprised both forces with a counterattack that drove them out of Kupres and its surrounding area. Its lyrical origins are unclear, but some unsourced claims state that it was written by an anonymous poet from Herzegovina. However, other sources contend that its authors were a small group of the Ustaše soldiers of Jure Francetić and Rafael Boban who sang the lyrics to the melody of the song "Oj kupreško Ravno poljce" (Oh Kupresian flat field), which is also about the Kupres battle. The lyrics, translated to English, are as follows:
Oj Kupreško ravno poljce,
Što pozoba crnogorce,
Od tisuću i pedeset,
Vratilo se samo deset,
Od tih deset kraj Prisoja,
Dočekala crna bojna,
A tih deset muku muče,
I po njima šarac tuče.
O Kupresian flat field
That consumed the Montenegrins!
From one thousand and fifty men
Only ten have returned.
And those ten? At Prisoje
They were awaited by the black battalions.
And those ten are racked with pain,
A machine gun still shooting them down
There are more than 40 verses in the original song, but only seven or eight are usually sung.
The seven or eight commonly known verses are these: