Which war is recognized as the first war of the twentieth century?

The recognition of World War I as the first war of the twentieth century is rooted in its significant global impact and the context of warfare at that time. Initiated in 1914 and lasting until 1918, this war involved many of the world's great powers and marked a major turning point in military tactics, international relations, and global politics.

World War I introduced new forms of warfare, including trench warfare and the use of advanced weaponry, which dramatically changed how wars were fought. Additionally, the war set the stage for many of the political and social upheavals that followed, reshaping national borders and leading to the eventual rise of totalitarian regimes in Europe.

In contrast, the other wars listed occurred later in the century or were not the initiating conflicts of the period. The Korean War began in 1950, World War II started in 1939, and the Vietnam War primarily occurred during the 1960s and 1970s. Thus, World War I stands out as the foundational conflict that defined the early twentieth century, justifying its designation as the first war of that era.