Thucydides, it's hard to fit a dog into an apartment. =/
Draugnar, you must have had a mutant Shih-Tzu. Or maybe I've got one, but mine definitely sounds like a small dog. She's also extremely aggressive and will attack much larger dogs. She usually comes out on top, but only because the other dog is just confused by the aggression. It's like if a kid just randomly started attacking you, you'd just be like "What the crap is happening? Can someone get this kid off me?" You wouldn't really kill the kid, you'd be more likely to try and retreat. Small dogs often have what I like to call Chihuahua syndrome (many small people too!) where they defend themselves by being overly aggressive because they can't afford to not be.
Also that is one hell of a Sebi, or one dunce of a Rott. My German Shepherds play-fight with each other a lot. Once a little beagle kept on nipping at one of my Shepherds and barking and generally being aggressive. My shepherd mostly tried to ignore it, like she normally does, but I guess this one pissed her off, because in one swift movement, like in half a second, she had flipped the beagle over and had her teeth at the beagle's throat. She didn't bite, but just showed that without a doubt she could kick that beagle's ass. I was just sort of standing there impressed, but the dog's owner started screaming at me, which I can totally understand.
My own Shih Tzu sometimes tries that aggressive stuff around my shepherds but it's funny. They usually just stick their snouts under her body and just flip her over. I imagine it's very frustrating for my Shih Tzu to have that happen over and over.