This is the next stage up the ladder towards more formal attire and would be appropriate for some icebreakers or dinner at the commander's quarters. For men, this means a sports jacket or blazer with color-coordinated slacks and tie. It can include three-piece suits as well. The civilian equivalent to our mess dress uniform is a dinner jacket or black tuxedo with black bow tie. Appropriate attire for the ladies would be long or short evening dress.
Many women suffer discomfort because they often buy shoes to fit the occasion instead of the feet.
For official functions, call the protocol office issuing the invitation. Be especially sensitive when developing itineraries for visiting dignitaries. Again, be as specific as you can, and always explicitly include both military and civilian attire on invitations when you want the military in uniform at a function with civilian guests. An evening dress is more elaborate with a lower cut back and shoulders exposed. There are several excellent texts on the subject.