This is an article a friend sent me the link to about knitting during World War I. I have been watching several BBC shows via netflix and I notice how many women knit in the series as well as the garments they make are shown…(Call the Midwife, is one series)
When my own son in law was stationed in Korea a few years ago, I knit him regulation color beanies for the cold weather. He told me that he always wore BOTH at the same time because it was so cold there!!
I have noticed in a lot of British made world war 2 films you see a lot of people knitting. One that jumps to mind is a film called the Battle of Britain were female Royal Air Force controllers (in underground bunkers, identifying when German attacks are coming) are seen knitting between air raids. From wartime biographies I have read, it helped people keep their mind off the fear of waiting to be attacked and therefore stay calm.
So…Keep calm and carry on knitting 
I have a couple of original 1940’s “knitting for the troops” patterns for hats,gloves, scarves etc.