Help! My 8 Month Puppy Attacked Another Dog!

Whilst i was walking the dog off lead at the local field, another dog smaller than him, approached my dog intending to play, posing no threat with it's body language from what i could see, and my dog tried to attack it! I was not nervous in anyway, this is completely out of character for my dog, he has always been VERY friendly, he growled at the dog before attacking, this is not like my dog to growl. I got in the way and broke it before something happened. I am posting this, not because i don't know what to do, but because i want to know why he has suddenly become aggressive. points to note- he will not allow other dogs to sniff his behind, he will only allow dogs to sniff his face? why?
- also note he has always been socialized with other dogs and has never shown aggression before, EVER!
-he always plays happily with with dogs that he knows and dogs he doesn't know.

Thank You

Hi
Its reallly impossible to say without seeing what has gone on here
What kind of attack are we talking about? growling? showing his teeth? air snapping? pinning the dog on the ground? drawing blood

I would head to the vets to check there is no medical problem with him first
and think about what happend - what was the other dog doing
No dog likes all dogs and if he dosent like his bum being sniffed then thats something to take into account
Have other dogs tried to mount him and hurt him? he might just be nervous of the dogs behind him cos he cant see what they are doing
How is he with other dogs?
Had anything else happened that day to make him more grumpy?

It is a VERY good thing that he growled before attacking - he was telling the other dog (and you) that he was not happy and wanted whatever was happeing to stop
the other dog didnt take the hint - so he had to make his point more obvious

In the future I would take the hint from my dog and get him out of there when he tells you he isnt happy

Hi, Thank You for replying
in answer to your questions, he growled and barked at the other dog, there was no blood drawn or pinning down of the other dog because i was quick to get in between. he was attacked by a staffie 3 weeks ago but has been fine with dogs since then so have i so there is no tension in the walks. i think some of his behavior relates to dominance?

ah it is possible he is more weary cos of the attack
I would discount the idea of dominance really, that isnt helpful - dominance is not dogs fighting or not liking other dogs or anything like that. It is likely a mixture of several things - possibly his age and hormones, the attack, how the other dog was being
and we have to remember that dogs, like humans, dont have to like everyone - the other dog could have been being really rude

thank you for the advice

If this was a one off, I'd be inclined to think that the other dog was potentially being very rude and sparked it off. Dogs can have scraps that sound like they are killing each other but it's often all noise and flying fur but nothing serious. Obviously you don't want this to get out of hand but I wouldn't panic just yet. Personally I would a) arrange some play sessions with dogs that you KNOW will be calm and polite to generate some good experiences after the attack and b) don't panic. Just monitor it carefully. It could just be a one off

Also, my dog has aggression issues with other dogs so I have spent a lot of time at classes and with trainers for aggressive dogs, discussing aggression. One thing I have learned that aggression by itself is not inherently bad. People are appalled if their dog shows any aggression but can you honestly say you got through life without ever losing your temper or shouting at someone? Probably not, and it's not fair to expect your dog too. I also learned that I tend to automatically blame my dog and it's not always him fault! Aggression is just a behaviour and a natural part of dog language. The vital difference is how much control the dog has. Obviously right out fighting, pinning, biting wtc is unacceptable. But I don't have a problem with a dog who wants to growl (warnings are very important communication), have a bit of a bark or even an air snap, as long as its within reason. Psychotic barking and lunging on the other hand is not good. It's about an acceptable level, in my opinion. I just don't think it's fair to expect a dog to never ever react. It may also help to start taking control of meetings and brushing up on general obedience, it's possible that the attack made your dog lose some confidence so it would be good if he can look to you to control the situation instead of making de idiots himself. HTH