Which war was fought by the U.S. during the 1900s?

The correct answer is World War I because it was a significant conflict that involved the United States and occurred during the 1900s. The U.S. entered World War I in 1917, alongside the Allies, and played a crucial role in the eventual defeat of the Central Powers. The war had profound impacts on U.S. society, politics, and the global landscape, marking a transition for the U.S. into a more prominent role on the world stage.

While the other wars mentioned also took place, they do not fit the question's requirement as they either occurred outside the 1900s or do not represent the leading historical milestones of that century. The War of 1812 occurred in the early 19th century, well before the 1900s. The Gulf War, which began in the late 20th century, was not part of the earlier 1900s timeline. The Korean War took place in the early 1950s, which, while still during the 1900s, is not as historically significant to the early part of the century as World War I. Thus, when considering wars that were pivotal and representative of U.S. military involvement in the 1900s, World War I stands