RETREAT, HELL! Extraordinary challenges face the Marines in Korea, in W. E. B. Griffin's most electrifying Corps novel yet.  It is the fall of 1950. The Marines have made a pivotal breakthrough at Inchon, but a roller coaster awaits them. The bit in his teeth, MacArthur surges across the 38th parallel toward the Yalu River, only to encounter the Chinese in full force, who drive him back in turn. Back and forth, the bloody tides of war shift, and swept along with them are Captain Ken McCoy and Master Gunner Ernie Zimmerman, caught in the fight of their lives; Brigadier General Fleming Pickering, working desperately to mediate the escalating battle between MacArthur and Truman; and Pickering's daredevil pilot son, Malcolm, lost somewhere behind enemy lines-and maybe lost forever.