How can I stop my 1.5 year old dog from attacking my 10 week old puppy

Aggression can escalate very quickly if the right intervention isn't taken. I strongly recommend that you contact a trainer/behavioralist for a consultation. They can identify the seriousness of the situation and give you instructions that will provide an easeful family setting. Until that is done, I would separate them when you are not able to provide close supervision and intervention.

I had the same problem with my lab/husky. He was fine with my dog that was older, but when we bought the lab puppy home bear would attack him by the neck. Diesel would just lay there. I would watch him very carefully to see why. Most of the time it was when food was involved or it he wanted to play. I kept my puppy in another room when ever I went anywhere until diesel got a little older. I also made sure I gave bear a little more attention.

I like a lot of the suggestions so far! I have one to add. I also have a new puppy. One of my older dogs loves him but one is acting similar to what you discribed. I just watch, some dogs growl when they are unsure and it's normal for the older dog to make sure the puppy knows 'who's boss'. I would wait a while, a couple of months at least before I left them out together. Is your puppy crate trained? LOTS of chew toys, so no disputes are necessary!

I have seen this before with my dogs. I think it is a mixture of jealousy and dominance. Maximus is probably feeling that he is getting less attention and the only way to get your attention is by showing agression towards the new puppy. Also, dogs are pack dogs but their is always a leader. It is important for him to feel like he is the leader. In a way this is ok, it will keep the puppy in line. But if he gets too agressive it is a real problem. So, my advise is to show Maximus ample attention. Make sure you keep time for just you and him. Take him on a walk by himself, play a game w/ him without the other dogs. The other things will fall in line. As for the nipping, never leave them alone until this is resolved. You dont want Maximus to get carried away. Hold the puppy on your lap while petting Maximus. Also, remember to keep the pup away while he is in his own spaces. It will work out in the end. Maximus will warm up to the new addition.

You have some good advice already. I would only add that it would be good to start giving your dog positive associations with the puppy. Feed your dog near your puppy. Give treats when the puppy is playing around him. In all, make it as positive as possible whenever they are together.