In early June, 1944, tens of thousands of American troops prepared to storm the beaches of Normandy, France. As they lined up to board the invasion barges, each was issued something less practical than a weapon, but equally precious: a slim, postcard-sized, softcover book.

These were Armed Services Editions, or ASEs—paperbacks specifically designed to fit in a soldier’s pockets and travel with them wherever they went. Between 1943 and 1947, the United States military sent 123 million copies of over 1,000 titles to troops serving overseas. These books improved soldiers’ lives, offering them entertainment and comfort during long deployments. By the time the war ended, they’d also transformed the publishing industry, turning the cheap, lowly paperback into an all-American symbol of democracy and practicality.

More: How Books Designed for Soldiers’ Pockets Changed Publishing Forever - Atlas Obscura