Bob Duggan also provides a detailed historical summary here. This includes Bannon's article and a collection of articles on more recent developments.
Robert Young's article in the Journal of Asian Martial Arts Vol 2, number 2, 45-69 (1993), and Willy Pieters' follow up in JAMA Vol 3, number 1 83-89 (1994) are worth reading.
The truth is that Hwa Rang Do, as taught by Master Kim, and as taught by Joo Bang Lee, and anyone else using the name, was devised in the 1950s, 60s, 70s from material researched, collected, refined and improved in Korea at that time. Some of that was as part of elite training groups in the Korean military (training body guards, covert operatives and special forces). Other parts were amalgams of generic material from Hapkido, Chang Moo Kwan, Ship Pal Gay, and other sources (especially for the weapons stuff). Tom Osborn - 2001.