Any time a horse joins an established herd, things get rearranged and the new horse has to find his or her place in the herd order. Pie is a laid-back, fairly submissive guy, and the only horse I've seen him move is Fred, and even then he isn't very aggressive about it - he just pins his ears a bit and Fred walks away. Fred has always been low man in the gelding herd, and it seems that Pie is just above him.
I watched the geldings carefully today at turnout to see if I could determine what was going on. Pie went out first, and went directly - he trotted - to the round bale and started eating. Eating seems to be a big priority with him - I haven't seen him play once. Then Fred and Fritz went out. Fred walked up next to Pie at the round bale, sniffed noses and started eating. A minute or so later, Fritz screamed and swung his hindquarters toward Pie and kicked him. Pie was moving away, but didn't move fast enough and got kicked again in the same hind leg - this time just a superficial blow that didn't bleed much. Then Scout came out. Fritz would move Scout who would move Pie who would move Fred - ring around the round bale. Fritz tolerates Fred pretty well - they have the same owner and have been together for years. This is a good thing as Fred is increasingly feeble and has trouble moving very fast. When I left the barn, they were all eating at the round bale, with Pie on the opposite side from Fritz and with Scout and Fred on either side.
I told Pie to try to move a bit faster - he never uses more energy than he has to and his head is buried in the bale so he's an easy target. I expect the bites on his rump are from Scout moving him or trying to play with him. Poor Pie! He doesn't seem too worried about things, though, and I hope he learns to stay out of Fritz's way - I expect he can't understand why anyone would be so nasty! Fritz isn't usually a very aggressive alpha, and I hope he relaxes a bit soon - he's also been pretty agitated in the stall both in the evening and the morning.