Yes. Adultery is a crime under the UCMJ. Such crimes are not always prosecuted, however, depending on what kind of impact the adultery has on the military service.
NOTE: The information above is intended as general legal information based on minimal information, and does not constitute legal advice. This information does not constitute communication with an attorney, nor does it create an attorney-client relationship or any of the privileges that relationship provides.
Yes. Also remember that because it it is a crime, a soldier has the the right to remain silent and seek legal counsel, Army Trial Defense Service or civilian legal counsel, under Article 31 of the UCMJ and should not make a statement or admit to anything without advice of an attorney.
While adultery is listed as a criminal offense in the UCMJ, it is very rarely prosecuted in a court-martial. The few times I have seen it referred to a court, the adultery charge was a minor additional offense included with other offenses. Adultery is prosecuted under Article 134, UCMJ. Art. 134 offenses include an additional element - that the adultery must be service discrediting or prejudicial to good order and discipline. This additional element is why adultery is rarely prosecuted in court. The UCMJ lists many factors for commanders to consider when deciding what to do with an adultery case. The usual factor that is most likely to have an effect on whether the case is prosecuted is whether the adulterous act had a direct impact on the mission and/or unit.
The military does handle adultery in other ways, such as administrative actions (letters of reprimand) or Art. 15 non-judicial punishment.
Lastly, if a soldier's command learns of adultery, command will often issue a no-contact order to the soldier (to each person if both are in the service). A violation of the no-contact order is where the soldier would likely face disciplinary action.