Why was the Battle of Midway fought?
The reason for Japan's move against Midway at this point in the Pacific war was all due to the Doolittle Raid in April 1942. It was this attack, albeit with little military significance, that "brought the war to the home islands of Japan". It demonstrated to the Japanese military leaders that the home islands were vulnerable to air attack. Therefore, their sphere of influence in the Pacific would need to be enlarged to prevent further bombing of the home islands. The Battle of the Coral Sea, in the southern Pacific, was an attempt to enlarge the sphere of influence in the South Pacific. Although the Japanese sank more gross tonnage in this battle, the Americans halted the expansion of the Japanese as Port Moresby did not fall to Japan has Japan had as an objective in this engagement. The next two objectives would be Midway in the Central Pacific and Dutch Harbor in the Northern Pacific. The Japanese did not know that the Doolittle raiders sortied from Pearl Harbor and quite possibly could have departed from the Aleutians. Therefore, Japan had a choice of Midway Atoll or the Aleutians as its next objective. Since the Soviet Union was not involved in the Pacific Theater at this point, the Aleutians seemed less a threat than Midway (The Americans would require assistance from the Soviet airbases for returning bombers to refuel to get back to the Aleutians if departed from Dutch Harbor and bombing Japan). Midway, known as "Pearl Harbor's Centurion", was much more appealing to the Japanese as it could be supplied easier from the west, as well as providing an air base for future bombings of Pearl Harbor. With Midway captured, there would be no way an American carrier group would risk navigating across the Pacific to bomb the home islands of Japan. At this point in the war, Midway was a logical objective for the Japanese. How they went about that objective is another story, however hindsight is always 20/20.
The U.S. did not a General. The battle was fought by naval forces, therefore, the leaders were Admirals. For the U.S., Admiral Nimitz was the commander in chief, US Pacific Fleet and he was stationed in Pearl Harbor. Admiral Fletcher and Admiral Spruance were the U.S. leaders at the Battle of Midway.
Taking place in June of 1942, the Battle of Midway was fought because of the Japanese decision to follow its initial successes in World War II with still more. Taking Midway would be another step for the Japanese towards total victory over the United States. At the same time, it would secure a base that could prevent U.S. forces from being able to attack the Japan home islands undetected and unopposed.
You probably mean what if the battle didn't happen. Well, there was a war going on, wars consist of battles, or else the war would be over. So, considering there was a war going on, Midway would have been fought sooner or later...maybe somewhere else other than Midway...but it was bound to happen sooner or later.