How to spy on http requests behind the scenes

When I run "docker pull..." it queries the appropriate registry, which redirects the request to (in my case) an S3 bucket. But I don't see any of that in the docker pull, of course. It handles all that in the background. How can I see what kind of http requests are going on from this command? Preferable just the ones associated with this process, but even if it were everything at the moment, that'd be fine.