By late last week, President Donald Trump had decided to fire Gen. Charles Q. Brown, the chair of the Joint Chiefs of Staff, and replace him with one of two very different candidates, according to two administration officials.

One was Gen. Michael E. Kurilla, a hard-charging Army four-star general who oversees U.S. military operations in the Middle East, one of the Pentagon’s highest-profile assignments.

The other was a little-known retired three-star Air Force officer, Dan Caine, with an unorthodox career path that included time as a fighter pilot, the top military liaison to the CIA and an Air National Guard officer who founded a regional airline in Texas.