What can I do if my salary was cut without any legitimate reason?

To answer this question, an attorney would need much more information regarding the facts of your situation. Specifically, you likely have a detailed employment contract that addresses your rights in this regard. It's possible that your employer's word that your salary could not be reduced except for in certain circumstances (such as a reduction for all employees) could be interpreted as a modification of the employment contract, but it's likely that the employment contract itself explicitly prohibits oral modifications. In short, of course, you are being taken advantage of, there's little doubt of that. International contractors are often subjected to such tactics by their employers. However, there's also little that can be done easily to remedy the situation, especially while you're deployed in-country. That's not to say, though, that nothing can be done. If there are such a substantial amount of individuals who have been affected by these cuts, you should organize together and retain an attorney to investigate and pursue any available legal options. It's possible you might have little ultimate legal recourse, but it's also possible that you may be able to recover the amount you've been shorted.