Smaller/Young dog attacking older dog

Could be a pecking order issue. I had similar problem when i got a 3 yr old cattledog as companion for my 13 yr old german shepherd. Shepherd was stone deaf and not very agile anymore. Cattledog was attacking him at certain points around the house. Food and water bowls, doorways.. I got a dog trainer in who showed me how to put the cattledog behind me in the pecking order. Apart from the obvious feeding them separately out of sight of one another, there were 2 things that made all the difference. 1. Tie up the newer dog across the room and pet the other dog bigtime in view of the new dog. Then switch it around. But the most effective was the snailwalk.
Leash the new dog. Hold the leash so he is close to your leg. Walk VERY slowly..super super slow..around the house..specially those points he is attacking in. He will hate it. If he wriggles around ignore it. Dont look at him. If he sits down ignore it. Keep up the SLOW walk til he is walking SLOWLY beside you. He will pant, lick his lips, ignore it. Do this for about 20 mins. Then, tell hum to sit, pat him firmly on the head, let him off leash and goabout your business. Dont look at him. I did this daily for about a week. Different dog.. Much more relaxed and much happier.

I had the same issue. I had a 14yr old Pomeranian and 4yr old Maltese. The little one would bark at the old one, snap and snarl too. I think dogs does not understand being old and that we should care more. I came to conclusion that the little one is showing those behaviors because she knows that she is stronger than the old one. Very sad.

I have a same experience too. I just cared more to the old one, since my older dog was weaker and I knew that I haven’t got much time left, but this worsen the situation. Younger one was so jealous and acted more violent towards the old one. So be careful!