The GALVANIC operation did not use pre-positioned fire support bases on nearby small islands for valid reasons. The Japanese still posed a significant naval threat, and indeed their plan was simply for the land defenses to fix the American fleet in place for a yogaki ("waylaying attack" or ambush) by naval forces. In fact, US amphibious doctrine emphasized quick capture to avoid a counterstroke against vulnerable and stationary transports.
The US Army's 165th Infantry reduced Butaritari (Makin Atoll) slowly and systematically with few casualties, but the yogaki - submarine I-165 - sank the USS Liscome Bay. More sailors died there than there were Marines killed on Tarawa. This was to have far reaching consequences, as it convinced Holland Smith that Ralph Smith's 27th Infantry Division was not up to the task.
After Pearl Harbor the Navy was always afraid of another ambush. They repeatedly cut short bombardment and rushed the Marines in to take heavy casualties. Tarawa is one place a fire support base... more
to note that the Gilberts had to be taken. US carrier forces were never strong enough to project enough power, nor did they have adequate staying power to achieve uncontested air superiority or... more
I believe that both the Gilberts and the Marshalls could have been bypassed for the Marianas. The Gilberts and Marshalls were not easily supplied. Fighter raids would have destroyed air power in the... more