There’s no single, military-wide policy that specifically prohibits Service Members from engaging in consensual sexual activities while deployed. However, sex during deployment is a tricky matter because fraternization, wrongful cohabitation, and even adultery are outlined by the Uniform Code of Military Justice (UCMJ) as potentially serious offenses under UCMJ Article 134 of the Manual for Courts-Martial United States (2016 Edition). In addition, each specific branch has certain guidelines that define appropriate relationships between Service Members.
It’s also important to consider the potential negative effects to unit readiness and morale that can result from relationships among those who are deployed. Unintended pregnancy, compromised chain of command, and sexual misconduct are all possible outcomes that can impact Service Members and compromise unit performance.
Rabie, N. Z., & Magann, E. F. (2013). Unintended pregnancies among US active-duty women. Women's Health, 9(3), 229–231. doi:10.2217/whe.13.21
Manual for Courts-Martial United States. (2016). Retrieved from http://jsc.defense.gov/Portals/99/Documents/MCM2016.pdf?ver=2016-12-08-181411-957.