37 USC 305 - Special pay: hardship duty pay

(a) Special Pay Authorized.— 
A member of a uniformed service who is entitled to basic pay may be paid special pay under this section at a monthly rate not to exceed $750 while the member is performing duty in the United States or outside the United States that is designated by the Secretary of Defense as hardship duty.
(b) Regulations.— 
The Secretary of Defense shall prescribe regulations for the provision of hardship duty pay under subsection (a), including the specific monthly rates at which the special pay will be available.