How many Smokejumpers were killed in the 1949 fire at Mann Gulch as noted in the nonfiction book, Young Men & Fire?

In 1949, Mann Gulch was the site of a devastating fire that claimed the lives of 13 Smokejumpers, members of the U.S. Forest Service that routinely jumped from airplanes into the heart of a forest fire with the hopes of containing it or extinguishing the blaze.