expression
it can't be helped; there is no choice; inevitable
A somewhat formal or literary set phrase expressing resignation or acceptance of an unavoidable situation. Similar in meaning to 仕方がない but with a more classical, weighty tone.
戦となれば、是非もなし。
If it comes to war, it can't be helped.
是非もなし、運命に従おう。
There is no choice; let us accept our fate.
From 是非 (right and wrong; by extension, the pros and cons or the way things are) + も (inclusive particle) + なし (classical negative of ある, 'not exist'). Literally 'there is no right or wrong about it', i.e., the matter is beyond debate or choice.