I'm often struck by how alert, observant, and intelligent military working dogs look. The photo above offers one example. You can imagine the dog is saying to the soldier, "Dude, did you hear that sound?" or "Are you really sure you want to go through that door?" Or even, "Hey man, before you go through that door, aren't you supposed to follow procedure and communicate with your squad leader?" (In my experience, dogs like humans to follow predictable routines.)
In the photo below, from Okinawa in 1945, the Marine and his dog look equally worried, even stressed. The caption says the dog detected a Japanese machine gun nest waiting in ambush.