Is your husband an officer or enlisted and is the other female a military member?
Adultery could apply (Article ), there could be more, but I'd have to know the exact status of the female and your husband. Article 134, para 62 governs adultery.
There are three "Elements of Proof" for the offense of Adultery in the Military:
(1) That the accused wrongfully had sexual intercourse with a certain person;
(2) That, at the time, the accused or the other person was married to someone else; and
(3) That, under the circumstances, the conduct of the accused was to the prejudice of good order and discipline in the armed forces or was of a nature to bring discredit upon the armed forces.
How do you know your husband had an affair and what proof do you have of his sexual relations with this other woman?
The government must show that the individual's conduct had some direct negative impact on the military. This normally would include cases of fraternization (officer & enlisted) or a relationship with another military member, or a military spouse.
The "Explaination" section under this offense now requires commanders to consider the following factors when determining whether or not the offense of "adultery" constitutes a crime:
A) The accused's marital status, military rank, grade, or position;
B) The co-actor's marital status, military rank, grade, and position, or relationship to the armed forces;
C) The military status of the accused's spouse or the spouse of co-actor, or their relationship to the armed forces;
D) The impact, if any, of the adulterous relationship on the ability of the accused, the co-actor, or the spouse of either to perform their duties in support of the armed forces;
E) The misuse, if any, of government time and resources to facilitate the commission of the conduct;
F) Whether the conduct persisted despite counseling or orders to desist; the flagrancy of the conduct, such as whether any notoriety ensued; and whether the adulterous act was accompanied by other violations of the UCMJ;
G) The negative impact of the conduct on the units or organizations of the accused, the co-actor or the spouse of either of them, such as a detrimental effect on unit or organization morale, teamwork, and efficiency;
H) Whether the accused or co-actor was legally separated; and
I) Whether the adulterous misconduct involves an ongoing or recent relationship or is remote in time.
J) What this means is that many incidents of "adultery" may not be considered a punishable "crime" in the military, unless there is some kind of direct negative impact on the military itself.
Under the circumstances, it seems as if this is a iffy adultery case at best.