Fashion scholarship as a discipline is still its infancy, so the “firsts” just keep coming. This one, for example, is the first to look at W.W. I and what women wore while their men were away. Which fashions showed devotion to soldiers at the front? Which suggested the men had been forgotten? The show includes wartime uniforms, mourning dresses, and hats, plus pieces by Lanvin and Chanel never before seen in this country. —L.J.