Red templar - Paul Christopher

After nearly losing his life in Africa, retired Army Ranger and
historian John Holliday is ready for some R&R back in the U.S. But when
a disheveled Russian called Genrikhovich intercepts him in the airport,
Holliday's homecoming will have to wait.

Genrikhovich claims to know of a long-lost sword called Aos-the
companion to Holliday's own Templar sword. Holliday quickly finds
himself on a flight to Turkey, where he begins following a trail that
will lead him to the dark heart of Russia-where the ancient Templar
Order has secretly wielded power for centuries...