At the start of World War II, the US economy relied almost exclusively on imported rubber as the key material for making, among other things, tires for cars and airplanes. The dependency was well-known, but in April 1942, when Japan cut off the foreign supply, the US was unprepared. Synthetic rubber ended up being part of the answer, but the rest of the answer involved a lot of muddling through. Alexander J. Field tells the story in “The World War II US Rubber Famine” (Business History Review, Autumn 2025, 99: 365-390). Field writes:
There were simply no satisfactory substitutes for rubber in a variety of critical uses, particularly tire carcasses and treads, the ultimate end use of 70% of rubber inputs. The severe shortage of natural rubber that resulted adversely affected the ability of the US military to project force and contributed to the disappointing record of wartime manufacturing productivity. … During World War II, the United States never escaped the threat of running out of rubber, which stood as a sword of Damocles over the entire economic and military effort. In 1944 the country almost ran out of natural rubber and would have, had the war continued into 1946.
One fun fact: Apparently the original World War II plan had been to launch a counterattack across the English Channel in 1943, rather than the D-Day invasion of June 1944. But in 1943, the lack of rubber meant that there weren’t enough landing vehicles for a counterattack to work.
A second fun fact: During World War II, “The rubber famine led directly to the imposition of a 35-mph speed limit and nationwide gas rationing in a country that, in the aggregate, was awash in petroleum. The intent was not to save fuel but to reduce tread wear on the tires installed on the nation’s 27 million automobiles and 5 million trucks, almost all of which were otherwise forecast to be off the roads within two years. These restrictions made it more difficult for people to get to and from work, contributing to absenteeism, and impacted the distribution of products by truck.”
The rubber famine is of interest for its own sake. But in addition, it echoes modern concerns about the risks of excessive dependence on key imported products–and thus may offer some food for thought on those issues as well. There were three possibilities for dealing with the rubber famine: grow rubber domestically, build up a stockpile of imported rubber, or produce synthetic rubber. Here’s what happened with each one:
Efforts to grow rubber plants from the far East in the western hemisphere had not worked well in the 1920s, but there was a plant called guayule that was a promising alternative natural source of latex–substitutable for natural rubber in many applications, and better than rubber for some of them. In 1930, a then-obscure Army major named Dwight D. Eisenhower toured the guayule plantations of Mexico, and wrote in his report: “Should our sea communications with [Southeast Asia] be cut in an emergency, shortage of rubber in the United States would rapidly become acute.” Eisenhower proposed in his 1930 report a US program to subsidize guayule. but at the time, nothing happened. On March 5, 1942, the US passed the Emergency Rubber Act, sometimes known as the Guayule Act, to subsidize farming of guayule in the the United States. But since guayule plants take four years of growth before they mature and produce latex, the law made no contribution to the wartime effort.
The US made efforts to build up its rubber stockpile starting in 1939, as war loomed, but by 1942 the total stockpile was equal to about one year of use. One problem was that the powers-that-be in Washington, DC, insisted that imported rubber travel by ship from the far East to New York, by way of the Panama Canal, rather than offloading in San Francisco and having the rubber cross the US by train. Having ships go all the way to New York was slightly cheaper than trains, but as a result, the ships carrying rubber were unable to go back-and-forth across the Pacific as often–and growth of the rubber stockpile was limited as a result..
The powers-that-be in Washington viewed research efforts in synthetic rubber as an overly costly sop to petrochemical companies up through February 1941, and the created a program that ended up costing as much as the Manhattan Project to develop the atomic bomb. As it turned out, total production of synthetic rubber during World War II was roughly two years of wartime quantity demanded–or bout twice as much as the stock of natural rubber entering the war.
As Field writes, the synthetic rubber progrm has been “uncritically lionized” in most writing about World War II, as if it just burst into existence and solved the problems. But aas Field writes: “The eventual availability of synthetic rubber in quantity did not end the rubber famine. Synthetic had to be blended with natural in the manufacture of almost all products, and in some cases synthetic could not be used at all.”
Moreover, the synthetic rubber program depended on a gas called butadiene, could be produced from petroleum or from alcohol. Standard Oil and other big petroleum companies favored a petroleum feedstock, although alcohol-based plants were also started. Field writes:
The first butadiene plant was not completed until April 1943. All three of the big alcohol plants opened that year, and they produced far more than their rated annual capacity. Of the five petroleum-based butadiene plants, the three largest did not begin production until 1944, and consistently produced below their rated capacity. … Without alcohol-based butadiene, it is hard to see how D-Day could have gone forward in June 1944. In retrospect, it is not clear that petroleum-based butadiene was needed at all to win the war. Butadiene from isobutylene was cheaper in the long run because, even though plants using this input were more expensive to construct, required more complex engineering, and relied on untested processes, the feedstock (petroleum) was ultimately cheaper. Due to huge agricultural surpluses accumulated during the Depression, however, the opportunity cost of ethanol was far lower during the war years, an advantage augmented by the much lower capital requirements of the process using it to produce butadiene.
The US government ended up establishing the foundations for a commercially successful synthetic rubber industry in the postwar period, one using petroleum as the principal feedstock, as Standard [Oil] intended. Given that synthetic rubber would be needed during the war, it would have been cheaper and faster to have focused from the outset on ethanol as the feedstock. Standard Oil bears responsibility for the emphasis on petroleum. Whether petroleum or ethanol was to be the feedstock, however, construction on the butadiene plants should have started earlier …
If Eisenhower’s recommendation had been followed back in 1930, or if the US rubber stockpile had been built up more expeditiously, then synthetic rubber would not have been needed to win World War II. If production of synthetic rubber had been alcohol-based from the start, it could have ramped up more quickly. If more rubber had been available, then the war might have ended sooner if the D-Day invasion could have happened in 1943.
The broader lesson is that a serious discussion of critical imported materials should never be a last-minute, against-the-deadline affair. Moreover, a serious discussion will need to resist pressure from domestic companies with a financial interest in the choices made. The US and Allied forces muddled through the rubber famine during World War II, but it was a nearer thing than most people realize. Field notes: “In 1945 the War Production Board forecast that, in the event of an invasion of Japan, the US would simply run out of natural rubber in 1946. Among other consequences, the US would then have been unable to manufacture airplane tires.” That fact surely played a role in the decision to use the atomic bomb.











