I brought home Kara my new SchH3 female (5 years old) GSD and introduced her to my 4 other dogs. 1 Labrador Retriever(female)(6 years old), 1 Australian Shepherd(female)(4 years old), 1 German Shepherd(female)(3 years old) and 1 German Shepherd(male)(5 years old). The Labrador and Aussie are both spayed. The three German Shepherds are unaltered(this might matter). Anyway, everything went well. Kara got along well with all my dogs with no problems. They played, slept, and did everything together. I just got done taking all the dogs on a walk together, and when I got home, I gave Kara her tennis ball. My Aussie went near her and out of nowhere, Kara attacked her not in a dominate way, but in a very aggressive way. I managed to separate them, thank goodness no dogs were injured. The next day I did my usual routine and let all the dogs out together. As soon as Kara and my Aussie saw each other, both dogs got into another huge dog fight out of nowhere. I thought to myself, what is going on. So me and my husband put each dog on a leash and took them to a quiet spot away from all the other dogs. We noticed alot of aggression from both dogs as they got close to each other. I have no clue what had happened. I have tried to show them both it's ok, but every time they would see each other, or get near each other, they would always try to fight. I now had to keep them separated. So another day when I took just the 4 dogs on a walk, Kara and my other female shepherd suddenly got into a huge fight. Same thing that happened with my Aussie, happened now with my other female German Shepherd. I now have to keep them separated. Another day I had Kara in the front yard while the other dogs were in the backyard. Kara managed to escape into the back. As soon as she saw the Aussie, they got into another fight. The other female German Shepherd jumped into the fight only attacking the Aussie. My female Labrador and male shepherd stayed away. I broke up the fight. As soon as things calmed down and when the Aussie and other female German Shepherd (Kia) met again, they never fought or never showed any aggression towards each other. They play like they always have. But every time Kara see's or get's near the Aussie or other female shepherd, will go crazy and try to attack them. To this day, I cannot get Kara to get along with the Aussie and other shepherd. Kara is totally fine with the female Labrador and male shepherd and has never had any fights, or showed any aggression towards them. The male shepherd sadly has passed away, so the only dog Kara can play with is the Labrador. They get along so well and have never had any fights, and Kara has never attempted to fight her. When it comes to the two other dogs, Kara will do anything she can to get a hold of them. Also now she is very aggressive with other big dogs. When Kara meets a small dog, no problems at all. She LOVES small dogs and only loves the Labrador. I understand Kara being highly trained in protection might be the problem, but I still don’t understand. This is a weird situation and I just need your thought on it. Thanks.