DoD employees, is it possible to reach a .mil website from a network that is not NIPR and without the use of a VPN?

Teleworking and trying to access some army .mil websites for training and some other stuff. Every time I try to go to a site, I get an error saying "this site can't be reached". Is there anything I can do to fix this, aside from using a VPN? I am using my regular xfinity internet connection.