Question: Why did Gordo bring up the horse thing at breakfast?
Answer: Gordo was making a point to Norman that the crew of the "Fury" had seen some horrible things during the Battle of the Falaise Pocket. After wiping out an entire German army there, they were tasked with putting wounded horses out of their misery. The point was that Norman was not there, and did not experience what they had, so Norman could not judge the tank crew's actions.
Gordo brought up the horse thing because him and the other (original) crew members were not happy with Don and Norman enjoying a nice, quiet meal without them. He even say's "You weren't there" meaning Don sharing this with Norman when he hadn't yet been through much war time like all of them had, together. They also say "We weren't invited", "Why weren't we invited." The horse story was to get at Don for not inviting them and sharing it only with Norman.
Chosen answer: Chris has "shooter's strawberries" on his elbows, which are red callouses caused by lying in the sniper's position for long periods. He notices the same marks on the elbows of the father, and realizes that he too is a military sniper.
Sierra1 ★