Japan intentionally built bases on many islands in the Pacific to extend its defensive perimeter, and the U.S. had to take over those bases one by one to be able to come close enough to the Japanese home islands to mount an invasion.

The decisive part of any invasion is not the getting troops to the beaches part; it's the supply needed to keep them there and keep them fighting (this is why the Guadalcanal campaign took so long, on both sides). Throwing an invasion force across the north Pacific straight to Japan without whittling down Japan's defenses in the central and south Pacific would have been an enormous waste of resources, because the Japanese would use their island bases to attack and disrupt supply lines supporting that invasion.

There is a rule of thumb I remember reading (but don't recall where, unfortunately) that originated during WWII among the quartermaster corps that said something to the effect that the difficulty of an amphibious landing increases by the square of the distance traveled. The longer you have to travel before hitting the beaches, the more problems.

These problems include the natural difficulties of a landing: managing the logistics of getting everyone into the right place at the right time, ensuring firepower support, making sure the follow-on logistics are in place, etc.

These problems also include the enemy. The longer your supply line to a beachhead, the greater the chance the enemy will be able to interdict it.

There were several major factors that precluded "going straight for the home islands." The first is that the United States was simply outnumbered at the outbreak of war. The attack on Pearl Harbor was devastating to the Pacific Fleet and forced the United States into a defensive posture; the Japanese had the initiative. At Guadalcanal, the first significant American counterattack, the Japanese and Americans traded naval superiority around the island. The United States, at that time, lacked the numbers to hold the waters around an island thousands of miles from the Home Islands. Starting in 1943, with the completion of ships planned in 1938 and 1940, that situation changed. In addition, fighting in the first full year of the war whittled down the Japanese Navy: As the IJN's numbers declined, the USN's numbers were rising.

The second issue is one of firepower support. A direct assault on the Home Islands would have lacked air or naval gunnery support in large amounts. There was no friendly airfield nearby to provide air cover for such a landing, and any air cover would have been provided by aircraft carriers -- which had far fewer aircraft than land-based airfields could support. Moreover, the attack on Pearl Harbor had drastically limited the number of U.S. Navy ships available to provide gunfire support.

The third issue is one of logistics. In 1941 and to some extent 1942, the U.S. Navy and Marine Corps lacked the logistical capability to land a large force on a hostile shore. Not until 1941 did Andrew Higgins and his company design a landing craft with a front ramp. As Gen. Eisenhower was to say: "Andrew Higgins ... is the man who won the war for us. ... If Higgins had not designed and built those LCVPs, we never could have landed over an open beach. The whole strategy of the war would have been different."

In addition to the Higgins Boats, the United States lacked expertise in combat landings. At Guadalcanal, for example, soldiers found trouble because the supporting freighters had not been combat-loaded. Critical materials including ammunition and weapons were at the bottom of the freighters' holds. When the freighters were driven off by Japanese ships, the soldiers on Guadalcanal were left outgunned and undersupplied.

The fourth issue is one of politics. If you read the (short version) of the U.S. Marine Corps history of the Pacific War, you'll see how much politics played into the situation. Starting in 1942, Admiral Ernest J. King, commander in chief of the U.S. Fleet and Chief of Naval Operations, argued for a drive across the central Pacific in order to capture the Marianas islands. The capture of these islands would put Japan in range of American bombers, and submarines based in the islands would cut Japan's supply lines farther south.

This idea was opposed by Gen. Douglas MacArthur and (more importantly) the British and Australians, who were afraid such a drive would suck resources from the Atlantic and the war against Germany. Australia in particular wanted a drive through the Solomon Islands and New Guinea to relieve the threat of Japanese attack on Australia. By the time of the Casablanca Conference in January 1943, operations in Guadalcanal and other points of the Solomons were already underway, and the Australians and British believed the appropriate strategy was to continue the drive up the Solomons. MacArthur supported this because such a drive would happen in his area of operations and would be in line with his goal of returning to the Philippines (King and many others were unaware of MacArthur's goal at this point).

A compromise was reached: the central pacific drive would be small in scope to maintain pressure on Japan in that area and divert attention from the main push up the Solomons.

Through the next two years, MacArthur would again and again successfully exert pressure and undermine the U.S. Navy's proposals for a drive through the central Pacific in favor of his own goal of returning to the Philippines. In hindsight, the Philippines campaign was completely unnecessary. The capture of the Marianas in 1944 cut off Japanese supply lines to points farther south, and the campaign in the southwest Pacific was largely irrelevant to the outcome of the war.

Had the United States supported the Central Pacific strategy from the start, I believe the war could have been shortened by as much as a year. In the end, political pressure was the key point that forced a split effort.

As others have noted it simply isn't possible to stage a major landing without an abundant store of nearby supplies. Just the short hop from England to France for the Normandy Invasion was a tremendous feat. Trying to go from Hawaii to Okinawa with thousands of miles of unsecured supply lines would be suicide.

The US had to retake the islands for exactly the same reason Japan had to take them in the first place. Land based planes from the Philippines would cut Japan off from oil. Without oil Japan could not effectively wage war.

Another major factor is the Germany First strategy. The US dedicated itself to a defensive war in the Pacific until Germany was defeated. Then the combined might of Britain and the US would be used to defeat the Japanese. Because most of the US effort was going toward Germany there simply wasn't enough manpower or supplies to launch an attack on Japan's major strongholds. Midway went a long way toward balancing the power in the Pacific but it took till 1944 for the US to truly have a truly dominant fleet in the Pacific.

Here's a nice site with the Pacific naval battles all in one place If you scroll through the battles and campaigns you'll see that for much of the war the US was the underdog able only to sortie out and barely hold against the Japanese before limping back to Pearl Harbor.

Guadalcanal wasn't supposed to be a six month battle. 14,000 Marines were supposed to land and quickly overwhelm a force of at most 6,000 Japanese. The island was important because land based planes on the island would be able to disrupt the supply route to Australia making ships take a much longer route.

For Peleliu I'm inclined to agree that it was a terrible decision. The airbase could have been neutralized with naval gunfire and the island bypassed. The US can be excused for not knowing how Guadalcanal would turn out in 1942 but by 1944 they should have known better.

The US island hopping strategy enabled them to bypass more Japanese than they fought. Islands were they didn't have to fight like Peleliu. You've probably never heard of most of the islands where Japanese troops were left stranded able to do nothing but watch US planes patrol overhead and hope for a submarine to bring some supplies and rescue maybe a few hundred of them.

Two things here:

The U.S. did not have an overwhelming advantage over the Japanese until after the halfway point of the war in '43. By the Washington and London treaties the U.S. and Japan had fixed a ratio for capital ships of 10 to 8, 3:2 for heavy cruisers, and a tonnage ratio of 7:5 for light cruisers. Since the US Navy was split between the Pacific and Atlantic, this meant that the Imperial Japanese Navy had a substantial effective advantage to start with, and after Pearl Harbor, an enormous advantage in battleships.

Two, the Pacific is truly vast. It's 4000+ miles from Hawaii to Japan, and 5000+ from the West Coast of the U.S. To invade Japan from the U.S. directly would be far beyond the U.S. capability at any point. To do that, you have to bring the entire attacking force, plus enough naval force to defeat the entire Japanese navy, plus enough aircraft carriers to carry enough fighters to beat the entire Japanese air forces with none of the Japanese forces being attrited by battle.

The U.S. used all those resources to attack small islands because it's easier to build an airbase and use land aircraft to whittle down defenses of the next target while using the new island to build up supplies for the next jump. In each case, the resources used represented the best effort available by the U.S. It would have been impossible to take the Marianas until '44 because there just wasn't the ability to move multiple divisions for an amphibious invasion and keep them supplied until them.

From Dec 1941 till about Fall 1943 the US in most cases DID NOT have numerical or tactical superiority over the Japanese at sea, or in the air.

They had fewer carriers, and fewer planes, and a sever shortage of tankers meant that the older battleships that were left couldn't be used and the newer fast battleships were just being launched.

As for Guadalcanal in particular the US could not afford to have a major enemy base with easy access to the shipping lanes to Australia, Rabaul was bad enough.

Finally the plan you suggested is essentially what Japan's hope was, to draw the USN in far from bases(because they hadn't stopped to capture any) and defeat them and pick off ships on the way and stragglers after. It is also much easier to keep a fleet fueled and supplied when you dont have to carry everything with you.

The various iterations of War Plan Orange really wrestled with how much time would be spent in securing bases and the resources needed for that, since they assumed it would be a race to relieve the Philippines. Eventually it sort of became accepted that moving deliberately and building up a secure base structure, even at the expense of the fall of the US forces farther West, was worth it to better leverage US industrial power.

I would recommend: Neptune's Inferno: The U.S. Navy at Guadalcanal by James D. Hornfischer

and

War Plan Orange: The U.S. Strategy to Defeat Japan, 1897-1945 by Edward S. Miller