The 1940's in Britain was a high point for hand knitting. Women on the home front could make a contribution to the war effort by knitting for the troops using patterns that were often given away free. Many specialized patterns developed such as the balaclava helmet with ear flaps for use in telephone operations or the mittens with a separate forefinger for firing a trigger in the cold.
There is a resurgence of using vintage knitting patterns. Victoria and Albert Museum, UK, has this page dedicated to such patterns.
Even this Helmet Cap would be useful in today's society.