Instructions
Take the dogs for a walk. Have a helper so you can handle one dog while the other is controlled by the other person. Keep the dogs far enough apart to prevent them from attacking each other, as dogs can be more aggressive when on leashes.
If the dogs appear to be calm, allow them to sniff each other. Look at their ears and tails. If the tails are up and the ears are forward, the dogs should be more relaxed and more apt to be social. If its tail is tucked and its ears are back, a dog is stressed and should not be placed in contact with another dog. Keep the dogs on leashes to separate them if necessary. This also will prevent mounting, an act of dominance that can lead to fights.
If they will stay in the same space, bring the dogs into the house. One dog may snap at the other in warning -- it is trying to establish dominance -- and this should be accepted, as long as they do not fight.
Notice which dog appears dominant. When handing out treats, give that one a treat before the other and generally give it attention before the more submissive dog. Both dogs will accept the hierarchy and this will help them to be more peaceful.
How to Socialize Two Male Dogs
Dogs are pack animals by nature and they establish a dominance hierarchy early, with one dog becoming the pack leader. This tendency remains in domesticated dogs. While a dog will accept you as a pack leader if you exert authority, it will compete with another dog to establish dominance. Socializing two males requires you to understand and respect this process and that hierarchy, once it has been established..