Can Collectors be Upgrades before Historian?

We have a rather large system with 2 historians and about a dozen collector machines all running on 23.2.1. We're looking at upgraded to the latest version. Do we have to upgrade Historians to v25.4 first and then Collector machines? Or can Collector machines be done first (since that's easier)? Is there a preferred or required order? I'm guessing Historians have to be done first so you can establish the new Identity service, right?