I loved how this season (and especially this episode!) tied together SO MUCH of Perrin's arc that we've seen so far. It really feels like this is the moment it's all been building towards.
His wife's death. Violence is hard to control and may hurt people you care about. Running into the Tuatha'an. Nonviolence is another option, that takes a different kind of strength. His interactions with Dain and the Whitecloaks. People's intentions and their actions don't always agree; people can be twisted by grief to perpetuate cycles of violence, and the only way to break out is to choose to stop.
We can now look back on all of that as threads in the story of how he thinks about violence and non-violence - when to deploy violence and when to choose not to - leading him here:
Lord Perrin Goldeneyes, who knows that the Two Rivers must fight or be destroyed. Who wants to send Faile away to be safe but listens and trusts that she can handle herself in battle. Who makes a deal with Whitecloaks he knows might turn on him because he can see it's the only chance they have. Who desperately - desperately! - wants to kill Padan Fain but holds back because he knows he can save more lives that way.