If your camera is down for an extended period that would probably be enough of an alert?
If I was the attacker I'd start off by knocking the cameras out a few times to make you think they're unreliable.
That probably requires more forward planning and effort than most criminals will bother with.
I mean the best thing you can do as an immediate reaction is call the police. Otherwise, hope nothing personal is stolen and that you can use the footage to claim insurance.