In the 1940's, the biggest influence on womens' fashion was World War II. The war caused shortages and restrictions that impacted fashion design. The use of fabric was rationed by the government and extras like nonfunctional buttons, drapery, and cuffs were forbidden. The materials were needed for the military and the war effort.
 Hemlines rose, in the 1940's and ladies' clothes were utilitarian and simple. As women joined the military and took jobs in industry, they needed clothing that was functional. The military also influenced styles of the day with shoulder pads and the use of military type colors like tan, cadet blue, browns, and air force blue.
Read more about the fashion trends of the 1940's at:  http://hubpages.com/hub/Fashion-History-Design-Trends-of-the-1040s