If someone loves history, how (or where) would he find more people with the same interests?

My brother is a history buff. He loves to read about, discuss and debate the battles and events between the Revolutionary War and WWI. Unfortunately, there aren’t others in his circle who share this interest. How would he go about finding more people who also enjoy this? Are there online communities? Are there societies that might exist in his region who would get together for this? How would he find others who enjoy this as much as he does?