Ring wraiths vs. Balrogs

[TarElendil]

The nazgûl did not have that kind of weapons to kill balrogs. E.g. the morgul knife poisons you, but I don't think a balrog can be poisoned like Frodo was. The swords that the nazgûl wields are hardly powerful enough to harm a balrog.

sorry, wrong.
"The black horses were filled with madness, and leaping forward in terror they bore their riders intot he rushing flood." STRAIGHT from the text. "Flight to the Ford" read it