τοῦ δὲ πολέμου οἱ καιροὶ οὐ μενετοί → in war, opportunities won't wait | the chances of war will not wait (Thucydides 1.142.2)
εἴην: εὐκτ. ἀορ. β΄ τοῦ ἵημι· ἀλλ’ εἴην εὐκτ. ἐνεστ. τοῦ εἰμὶ (ὑπάρχω).