So today Sister in law came over. She brought her new puppy (a darling 14.5 week beagle mix) with her. Diesel was scared but warmed up very quickly. Arwen and Strider were let in one at a time and Arwen checked out the pup and went into her feeding area (laundry room) and I shut the door. Not a peep from her (she loves puppies). Strider was doing that annoying bark. I wouldnt let him off leash as Diesel was so afraid. Diesel again warmed up quick and sniffed the air. He was wagging his tail and I slowly walked Strider over to meet him after Strider quit barking (no hackles raised or anything). I had a pretty tight leash on Strider. We were about 5 feet away and the puppy just sat down wagging his tail. Strider lunged and tried to attack him. Im not saying to check him out, Im saying full on lunge, teeth showing and very aggressive.) I immediately gave him a correction and kenneled him. He did not get the pup. But he sure as heck tried. The German Shepherd puppy we had here a week or so ago wasnt an issue and Strider got along with him great. Not an issue at all. But with Diesel, he just wouldnt calm down and even just sniff him. He was all out trying to eat him. What would you recommend me doing next time if this arises?? Im trying to socialize him with all different dogs and people. He is great with people so far.