chief doesnt have a aggressive problem but there is one dog in our neighborhood that he just doesnt get along with like to day (this isnt the first time with chief and this other dog doing this) lauren and i and ginger and this beagle came up to the porch and chief and the beagle and ginger are playing they're having a great time and her comes this older dog yellow lab and he is comming up slowly and he makes his way to the steps and chief doesnt notice him at first, but then he sees him and chief is wagging his tail ,but the other dog had his tail completely straight up and stiff and i dont know if that was a challenger or the two caught eyes but chief launches himself at the dog and there brawling showing teeth and all but as soon as i yelled no chief stopped and the other dog ran down the street (now a month or so ago i was walking my dogs had them on the leash and there is a neighbor that has a shepperd mixed with pyreness i think thats how you spell it and they love to play and here comes that dog i believe he lives next to that dog and he comes up and there visiting and seconds later he goes after chief and i break it up chief plays with the other dogs like nothing happened and then when we left and we were at the end of the garage they were fine sniffing each other) 2 wks ago they were running in my yard playing great no problems at all can someone please tell what is wrong with these dogs LOL