The surrender of Japan and the end of World War II were primarily influenced by several key events, but the most direct factors were:
A - U.S. bombing of Hiroshima and Nagasaki.
The atomic bombings of these two cities in August 1945 led to massive destruction and loss of life, which significantly weakened Japan's ability to continue the war. Following these bombings, Japan announced its surrender on August 15, 1945.
While the defeat of other Axis powers in Europe (B), the U.S. victory at the Battle of Midway (C), and the issuing of the Potsdam Declaration (D) were all important in the broader context of the war, the decisive moment for Japan's surrender stemmed from the atomic bombings. Thus, the correct answer is primarily A.