Final answer:
World War I was the major war following the Peace of Westphalia, starting in 1914 and ending in 1918. It was the first global conflict, involving advanced industrialized warfare.
Step-by-step explanation:
The major war that unfolded in the wake of the Peace of Westphalia was World War I. The Peace of Westphalia ended the Thirty Years' War in 1648, establishing the independence of the Holy Roman Empire's entities and marking a significant turning point in European political history. World War I, however, commenced much later, starting in 1914 and lasting until 1918. It was a truly global conflict due to its scale, the participation of countries from nearly every continent, and the industrialized nature of the warfare, which included advanced weaponry like machine guns and chemical gases. Although the war ended with an Armistice in 1918, the legacy of World War I and unresolved tensions contributed significantly to the onset of World War II.