Even a small pair of bolt cutters will walk through the toughest chain. A better thing to use is cable/wire rope. It's surely not going to stop them, but if armed only with bolt cutters it will, at least on their first attempt. Needless to say, they will most likely return with cable cutters or a portable cutting torch.
"Where there's a will, there's a way!" applies especially to thieves.
Something we use to protect our hunting camps here are motion activated lights in the area linked to audible alarms. The lights coming on seem to be a more effective deterrent than constant illumination and the alarms we use actually sound like Police sirens.
We also use game cams (motion activated with stills and video) to identify the tresspassers/culprits. We have the cams covering the area we wish to protect to catch them afoot hoping for faces for positive id's, as well as having them on access/egress routes to obtain info such as tags on vehicles, make, model, color, and the same info and/or registration numbers on boats.
Hope this helps!