@laquisha-ball , generally all transactions on an US base would be considered as US sourced because the base is effectively US territory ( for tax purposes ). The terms of agreement between US and Germany ( arms forces agreement ) on any earnings for services provided on the base , would dictate how it is taxed. My general opinion would be that this US territory and therefore not foreign income. However, if you provided similar service offbase and /or to German residents, then that would be outside the purview of this agreement and therefore eligible to be treated as foreign earned / self-employment income.
Does this help ?