Name one war fought by the United States in the 1900s. (65/20 version)

Wars fought by the United States in the 1900s (the twentieth century) include World War I, World War II, the Korean War, the Vietnam War, and the (Persian) Gulf War — naming any one is correct on this 65/20 civics question. The Civil War (1860s), the Revolutionary War (1770s–80s), and the War of 1812 all occurred before the 1900s, so they are incorrect for this question. Applicants should be able to name at least one twentieth-century war the U.S. fought. This question tests basic familiarity with major American military conflicts of the last century.