The Mexican expropriation of British and American properties in March 1938 marked the first time any oil-producing country successfully stood up to foreign companies who claimed to own oil properties in that country and who had the support of their respective governments. Totally reliant on overseas oil at a time when war seemed imminent, British officials responsible for policy toward Mexico immediately emphasized the importance of preventing other oil-exporting nations from following Mexico's lead. Washington also sought to make an example of Mexico—one that would guarantee respect for U.S. businesses operating abroad.

Although both Washington and London wanted to returban to the pre-expropriation status quo, Washington was unwilling to work with London to achieve this goal, and Washington's attitude paralleled its reaction to British efforts to get U.S. support on certain defense issues during this critical period. The resulting Anglo-American strife over how to handle Mexico was also consistent with Anglo-American commercial competition and the oil rivalry in Mexico early in the century.