The Second World War saw the company established as a national institution, and though it had no formal role, Penguin was integral to the war effort thanks in no small part to the publication of such bestselling manuals as "Keeping Poultry and Rabbits on Scraps" and "Aircraft Recognition" and supplying books for the services and British POWs. Penguin printed some 600 titles and started nineteen new series in the six years of the war and a time of enormous increase in the demand for books, consequently Penguin enjoyed a privileged place among its peers.