If Shakespeare's speech isn't well-known in your language or doesn't translate well, replace 'Unto the Breach' with a phrase that means something like 'Back into the fight!' or 'I'm trying this again!' with connotations of trying until you're successful.] In common, modern usage, 'unto the breach' basically means 'I'm going back into the fight' or 'I'm trying again' and can be used literally (like a soldier saying 'here I go unto the breach' if going off to war) or figuratively (like an office worker saying 'back unto the breach' when returning to work after a holiday). It also carries the implication that the soldiers will try again and again until they are successful - failure isn't an option.
The words themselves are now antiquated, but 'Breach' is just a type of gap or hole and 'unto' in this context means 'into', so it just means 'Fill up the hole in the wall!' meaning that the troops in the play will have to defend a gap in their defenses and defend it so well that the hole could be filled by their bodies.
