For an elite band of U.S. Marines known as the Raiders, the deadly military plane crash this week in Mississippi represents a second devastating blow during training in less than three years.

Six Marines and a Navy corpsman from a Raider unit died this week on their way to training exercises. All seven were from the Camp Lejeune-based 2d Marine Raider Battalion.

They are linked in tragedy with seven members of the same North Carolina-based command who died in a March 2015 helicopter crash off Florida.

"Our thoughts and prayers are with the entire Marine Corps Forces Special Operations Command (MARSOC) family at this time," said the MARSOC chief of staff. "The incredible demands of this dangerous and demanding calling forge some of the tightest unit and family bonds found in the U.S. military. This loss impacts us all."

The present incarnation of the Marine Raiders was formed in 2006 amid the global war on terror. The group was officially named the Marine Raiders in 2015 to link its heritage to World War II commando units made famous in movies.

The Raiders' commanders say the group has close bonds that make such losses devastating.