Which of the following events resulted in Keynes' development of macroeconomic principles?

While World War I had significant economic implications, it was not the direct catalyst for Keynes' macroeconomic theories. Instead, Keynes focused on the war's economic aftermath, particularly the Treaty of Versailles and its impact on European economies, which indirectly influenced his thoughts but did not solely shape his macroeconomic principles.

World War II did contribute to Keynes' ideas, particularly regarding government spending and its role in economic recovery. However, it was the lessons learned from the Great Depression that primarily motivated his development of macroeconomic theories, making World War II a less direct influence on his foundational principles.

The Russian Revolution primarily led to the establishment of a communist state and a departure from capitalist principles. While it may have influenced global economic thought, it did not directly result in the development of Keynes' macroeconomic principles, which were primarily concerned with addressing the failures of capitalism during economic downturns, as exemplified by the Great Depression.