During which global conflict did the concept of "Open Door Policy" regarding China emerge?

The concept of the "Open Door Policy" regarding China emerged during the late 19th and early 20th centuries, particularly in the context of the Boxer Rebellion and the scramble for spheres of influence in China among Western powers. However, it was primarily articulated by U.S. Secretary of State John Hay in 1899, which places its origin before World War I began.

World War I was characterized by the Allied and Central Powers’ military engagements and did not directly deal with the Open Door Policy itself, as this policy was already established prior to the conflict. Instead, it aimed to ensure equal trading rights for all foreign nations in China and to maintain Chinese territorial integrity.

The Spanish-American War occurred in 1898, which was a pivotal moment for U.S. imperialism but not directly associated with the Open Door Policy.

World War II, occurring later, continued issues related to imperialism and tensions in the Pacific, but it did not originate the Open Door Policy either.

Therefore, while World War I is the choice given, it is not the most accurate answer regarding the emergence of the Open Door Policy, which was actually developed before this global conflict.