[delacroix01]

「鬼に逢うては鬼を斬る。仏に逢うては仏を斬る」
I've just stumbled upon this line, and I can understand what it means, but I still need to ask a grammar question. Is 逢うては a conditional form in ancient Japanese (or maybe a literary form)? I'm pretty sure it means the same as 逢えば, but I think it's better to ask to make sure if I'm correct.