AC stolen - how to protect from happening again?

[Rivy S.]

I just did a pre-construction walk through on a property I purchased a few months ago.  The house had been broken into and the indoor and outdoor AC units are gone :( The outdoor unit was even in a cage, given that it's not a class A neighborhood, but they just sliced it open.  The property was vacated on June 1st, and when I did a walk through two weeks ago, everything was in order.  My question is, given that every property will likely have some periods of vacancy, how do you protect the outdoor AC unit from being stolen?

(Side note: I'm "lucky" the property has aluminum wiring, because they climbed up into the attic to try to remove the wiring from the house, but apparently realized that it wasn't copper and just removed a small section)