Combat pay is reflected on your W-2, Box 12, Code Q, Nontaxable Combat Pay. Your W-2, Box 1, Wages, tips and other compensation will not have the combat in this box since it is not taxable.
Your W-2, Boxes 3 or 5, will be higher, by the amount of your Combat pay because Combat Pay is not excluded from Social Security and Medicare Taxes.
Additional information: Combat Pay, Tax Style: Benefits When Serving in a Hot Zone