Final answer:
The Open Door policy, proposed by Secretary of State John Hay, sought to ensure equal trade rights among nations in China and prevent any single power from dominating trade. The policy was formalized through the Open Door notes, which emphasized free and equal access to Chinese markets for all nations, despite the initial lukewarm reception and varied enforcement capabilities.
Step-by-step explanation:
The policy issued by Secretary of State John Hay that allowed a nation to trade in any other nation's sphere of influence in China is known as the Open Door policy.
This policy was predicated on maintaining equal trade opportunities for all nations and ensuring that no single power could monopolize trade with China.
To this end, Hay sent out the Open Door notes in 1899 to other imperial powers that held influence in China, which stipulated that all nations should respect each other's trading rights and privileges.
Despite mixed responses and a lack of means to enforce the policy, the U.S. declared the Open Door policy to be the law of the land in China, which facilitated American goods to be traded throughout the nation and upheld the territorial integrity of China.
The policy issued by Secretary of State John Hay that allowed a nation to trade in any other nation's sphere of influence in China is known as the Open Door policy.
This policy was established in 1900 through a treaty signed with the Chinese government and aimed to ensure equal trading opportunities for all countries in China, without any one country gaining an advantage over the others. By implementing the Open Door policy, Secretary Hay sought to prevent the colonization and division of China by foreign powers.