Why did penicillin become widely used during World War II?

Penicillin became widely used during World War II primarily due to the successful development of large-scale production techniques, which addressed the initial difficulty of isolating the drug in sufficient quantities.12

While Alexander Fleming discovered the antibacterial properties of Penicillium in 1928, it was not until over a decade later that Howard Florey and Ernst Chain at the University of Oxford successfully purified the substance and demonstrated its clinical potency.132

To meet the urgent needs of the war, researchers collaborated with the United States Department of Agriculture to scale up production. By utilizing deep-culture fermentation vats and a more productive strain of mold—Penicillium chrysogenum—scientists and pharmaceutical firms were able to manufacture the drug in adequate amounts by 1944. This breakthrough allowed penicillin to revolutionize the treatment of serious bacterial infections among Allied troops and patients globally.123