Tesla CEO Elon Musk made a welcomed appearance at the 1st Marine Raider Battalion Ball and delivered a sobering speech that took many US Marines by surprise last Friday.

The 1st Marine Raider Battalion out of Camp Pendleton, California, is comprised of elite Marines under the command of Marine Corps Special Operations Command (MARSOC), the Marine Corps’ expeditionary force that typically operates in austere conditions.

Musk was invited to the event as a guest of honor because the Raiders wanted an “equally innovative” keynote speaker to honor the battalion on its birthday, a former Marine Raider commander who asked not to be named, told Business Insider. Around 400 people attended, including World War II veterans and Gold Star family members, the Marine Raider said.

Much like the secrecy of the Marine Raiders’ operations, Musk’s appearance at the event was closed to the press and kept low-key in order to “avoid a media frenzy,” the Marine Raider said.

Like other branches of the military, formal military events are steeped in deep tradition. The Marine Corps, however, pride themselves in being a distinct group from the other branches, and their customs were reportedly noticed by Musk.

Read the whole story from Business Insider.

Featured image courtesy of Joe Musselman.