Which war was fought by the United States in the 1900s?

The Vietnam War is indeed one of the significant conflicts involving the United States during the 1900s. It was a prolonged war that lasted from the late 1950s until 1975, which makes it a pivotal event in U.S. military history. The war was characterized by its contentious nature both domestically and internationally, as it engaged various factors ranging from Cold War dynamics to anti-war sentiments in the United States.

It is important to note that the other wars listed, such as World War I and World War II, are also significant conflicts involving the U.S. in the 20th century. World War I occurred from 1914 to 1918, and the United States entered the war in 1917. World War II lasted from 1939 to 1945, with the U.S. entering the war in 1941 after the attack on Pearl Harbor. The Gulf War, which occurred in the early 1990s, is another significant military engagement.

While the Vietnam War is an answer, recognizing it as part of a broader range of conflicts the U.S. engaged in during the 1900s is essential for a comprehensive understanding of U.S. military history.