In the history of the United States, times of national crises, such as World War I and World War II, feature domestic tensions. Such tensions are often due to a widely diffused fear of subversive actions within the country that aim to undermine the U.S. military commitment or destabilize the nation. Hence, patriotism has played a key role in testing loyalties and has been used as the basis for conducting surveillance on those considered to be potentially disloyal. Immigrants and ethnic minorities, in particular, have often been singled out for such tests of patriotism and surveillance, being accused of maintaining loyalty to their homeland and importing radical ideologies. Furthermore, state surveillance has sometimes melded with mob action and citizen vigilantism to prevent potential subversive actions.