The “getting between” maneuver is very common dog behavior, especially in a pack situation.
It serves to “defuse” an oncoming battle between two of its pack mates.
That’s why I stepped in as a “surrogate dog” in PetSmart.
The Husky recognized it for what is was and laid off his attack.
Any number of factors could explain the “sudden” aggression.
Some kind of subtle pain, shifting hormones [even in neutered dogs] and it could simply be put down to becoming an “old crotchety coot”...:)
I adivse *everyone* who has a dog who “suddenly” displays abnormal behavior to have FULL tick panel run.
Tick borne diseases account for a very high percentage of “sudden personality changes”, as can elevated liver enzymes and thyroid issues, oddly enough.
Bless you for keeping the old guy around, anyway...:)
Oh man, I had a sweet little lab whose personality changed like that. She never ran to attack out of the blue, but took great offense if a strange dog “got up in her grill” as dogs do to get acquainted.
Her necropsy turned up a liver dark and hard as a stone, according to the vet who did it. (Her liver levels got checked every year beause she was on anti-seizure meds, but the last test was not particularly alarming.)