Not sure what you are talking about.
For Federal taxes, IF you were in an actual combat zone, you just enter your military W-2 and all the boxes it has. box 1 shown will already be reduced by your combat pay amount (or more if you have other pre-tax deductions), the Combat pay will also be noted in box 12 of the W-2 with a code letter "Q", and that takes care of it. BUT, any other income you have (Interest, dividends, spouse's W-2, investment income) may still be subject to being taxed.
As far a state taxes are concerned, your state won't tax the combat pay either, and some state's won't tax you at all if you are posted out of your HOR/SLR state, while other states will tax all your non-combat income no matter where you are posted....but that's handled during the TTX software interview as long as you go thru it carefully.
Being in the military does not make you exempt from paying federal taxes. If you were in a declared combat zone for a period of time in 2019, and qualified for any type of tax exemption because of that, the exempt amount will be shown in box 12 with code "Q".
Now some states will exempt active duty military from paying state taxes if certain specific criteria are met - and not all military meet those requirements either. But one requirement that seems consistent across all states that allow this, is that the military member be stationed outside of their residence state for the entire tax year.
Now there are 37 states that tax personal income. So there's no way for us to know what state you may be referring to - or if you're even referring to state taxes at all. You'll have to provide more details.