About half of US casualties during the invasion of the Marianas took place while seizing Saipan. I know that hindsight is 20/20, but would it have been possible for the US to bypass Saipan and only take Guam and Tinian? Only one of the USAAF's six big airfields was on Saipan, and Guam's Apra Harbor was the main deepwater port in the Marianas. It seems like leaving Saipan to wither on the vine would have made more sense for the United States.
I expect it was necessary.
Saipan was so close to Tinian (5 miles) that when the marines assaulted Tinian, their initial artillery support was from batteries actually located on Saipan. North Field on Tinian would have been within range from Japanese Type 96 howitzers, making it unusable. This map shows where the artillery on Saipan was located that supported assault on the "white" beaches. If I remember correctly, everything north of the ridge line between Mt. Maga and Mt. Lasso was within range of the American M2 105 howitzers. The entire island was within range of the M2 155 "Long Tom" howitzers. The Japanese Type 96 and the American M2 105 had similar ranges, so the Japanese could have denied use of the northern section of Tinian from Saipan.
It might have been possible for the Americans to only take Guam. Taking Tinian though, necessarily required taking Saipan. It would have been unsupportable to have half the airfields within range of Japanese artillery.
