As a contractor working on a military base and if you receive a W-2 you would check "Worked outside the U.S. - I worked outside the U.S. for an employer that wasn't the U.S. government or its agencies" after entering your W-2. And you might qualify for the Foreign Earned Income Credit. Please see this FAQ:
https://ttlc.intuit.com/replies/3290703
Please see this IRS News Release for additional information:
https://www.irs.gov/newsroom/new-law-makes-clear-combat-zone-contract-workers-qualify-for-foreign-ea...
