A dog that was not properly socialized with other dogs when they were still puppies could show aggression towards others. There are times when a dominant dog has trouble with other dogs in their puberty years. Aggressive dogs are sometimes products of a bad experience. You can teach your dog simple friendly behaviors.
This includes sniffing buttocks of other dogs, wagging their tails, and move side by side. If your dog shows aggression, try to walk him parallel with the other dog while on a leash. Make sure that the dogs are close to each other. However, keep a good distance to prevent them from touching each other.
It is important that both dogs are exactly parallel to each other. No one should get ahead of the other. In addition, be careful not to tangle the dogs especially when you make a turn. Do these often until both of them relax.
When you show a change in their behavior towards each other, start walking them closer. This exercise aims to let the dogs find themselves friendly by socializing with a friendly dog. In addition, the exercise also teaches them that a dog approaching does not necessarily require aggression. This will require a lot of work but in a couple of months, you will reap your hard work.