Peter: when I clicked on your link, my (extremely sophisticated) protection software warned me not to proceed any further, so I didn't!

My advice re Tank and the JRT is that it is early days ... Tank is a bulldog, and you would be tempted to think that OK, he'll be boss, but probably not so. JRT's can be very dominant (that is not a popular word on this forum, so apologies to everyone who don't like the word), and you may well have just such a terrier. Tank obviously can squish him like a fly, but despite his breeding and size may well be a gentle, laid-back type of boy. My advice would be just allow them to settle, get used to each other, sort out their pecking order etc. etc. On a much larger scale, we had a very similar "problem" with our 2 boys, Tai and Ben. Tai was the resident rescue dog, had been with us for 2 or 3 years, when we rescued Ben. Tai is a registered utonagan, basically an Alaskan Malamute cross, Ben is an unregistered utonagan. Tai was about 7 or 8 when we took on Ben, Ben was about 5. Ben had had a very rough like of abuse and neglect. We have now had Ben for 2 years, and the 2 boys are inseparable. However, over the last 2 years they have had several extremely severe fights, during which injuries have been sustained requiring veterinary treatment. But we have pretty much allowed them to sort out who is boss between the 2 of them - each weighing in at 45 kilos apiece. It is Tai, and Ben has knuckled down now and they are like brothers. I am not saying that this will necessarily be the case with Tank and the JRT, but it could well be if you allow them to sort things out between them. You need to keep the faith, remembering that dogs will often fight seemingly to the death, but it is like a ballet, they duck and weave, all the time making the most ghastly noise but no actual damage is done, it is all sound and fury signifying nothing. The temptation to step in and separate is huge, but this can be a big mistake, and it all happens so quickly that it could even end in disaster. Us humans do not have the quickness of eye to be able to gauge whether things are OK or not.

The way I look at it is that you do not have much to lose. it's make or break for the little guy, but I would put money on Tank not wanting to seriously hurt him. It could well be that the JRT ends up boss - like my daughter's diminutive chihuahua, Gucci, who bosses Tai and Ben around like there's no tomorrow - 3 kilos against 45!!

Are they both castrated? Is one neutered one not? Or both neutered?

Gnasher, yeah you're right about Tank, he is laid back and is very submissive to me... the people at the Animal Humane said Harley was too, but it certainly doesn't seem like it... Tank just has so much weight and size on Harley that I'm worried if he did decide he didn't like the constantly snarling etc. that he might decide to eat Harley . I think you're right though, Harley is definitely gonna be the boss, LOL... I just want to make sure that they're eventually gonna make friends, cause right now it seems to really stress Tank out too.

They're both recently fixed, as well... Tank 2 weeks ago and Harley less (not sure exactly when) so their hormones could still be going strong too haha.

Submissive to you is great, but does not mean that he is or would be to other dogs. I would be worried by any dog that thought he was my "superior". I understand what you are saying re Tank, and that he is so much bigger and heavier than Harley, but this is not what is important ... as I say, little Gucci weighing some 3 kilos is the boss of my big boys, each weighing 45 kilos! He can growl at them, and they back off, turn away! The fact that Harley is being aggressive towards Tank, the gentle giant, could well be causing poor Tank stress, he IS a gentle giant and he is worried by Harley's aggression because it is unnecessary. Dogs have no idea of physical size - they do not think "gosh, you are so much bigger and heavier than me, I had better be respectful". They think the way they are ... dominant, or middle ranking, or submissive. This will be very unpopular on this site, but it is my opinion and the way I think things could be with Tank and Harley. I may well be so wrong, but it is likely that Harley IS the boss, rightly or wrongly, between the 2 dogs. This is nothing to do with your relationship with them both, you should be the boss, end of. But the way the 2 boys are with each other is independent of this and out of your control. The fact they are both neutered presents a level playing field, although my boy Ben is neutered, Tai is entire, but Ben was neutered very late at the age of 4 or 5 so he still tends to think like a full blooded male, showing interest in females in season, ladies underwear etc. etc.

Leave them be, within reason, poor old Tank may well be stressed out ... because he doesn't like the new boy on the block trying to overrule him, but at the same time he wants to squash him because he can ... if he is the gentle boy you know him to be, all will be well. Harley may well end up inside his mouth as a warning, but he won't hurt him. Gucci made the mistake once of pinching Ben's bone ... there was this muffled shrieking noise from inside Ben's mouth before Gucci emerged totally unscathed, none the worse but a good deal wiser!