For America, Guadalcanal was an unexpected and unplanned detour from its initial strategy in the Pacific in World War II but it provided an unexpected and rare victory during the first part of the war. It was also psychologically important as it punctured the myth of the invincibility of the Japanese soldier.
For Japan, Guadalcanal was also an unexpected event and a severe shock to the military, many of whose leaders felt it was the turning point of the war.
From December 1941 to May 1942, Japanese forces ran amok in the Pacific and Southeast Asia, capturing Burma, Malaya and Singapore, the Dutch East Indies (today's Indonesia), the Philippines, Hong Kong, islands across the Pacific as far east as the Marshalls and Wake Island and occupied the northern shore of New Guinea.
The next move by the Imperial Navy was to occupy the Solomon Islands chain, southeast of New Guinea, as the first step in a campaign to cut the supply lines from the United States to Australia. The next steps were to be the occupation of Fiji, New Caledonia and Samoa.
Although in early June, the US Navy, relying on decoded Japanese naval communications, sank four Japanese carriers at the Battle of Midway, the Japanese Navy still remained dominant in the Pacific. But the support of the Japanese Imperial Army was minimal for the Pacific Campaign. The Army's focus remained the war in China which had been going on since 1937* and the Army only released a small number of troops to support the Solomons offensive, thankfully for the US.
Image from The Daily Mail UK
On June 8, 1942, the Japanese landed a small force on Guadalcanal to begin construction of an airfield designed to help interdict American supplies to Australia.
America's original strategic plan in the Pacific was to delay offensive military action until its fleet of new, larger aircraft carriers began to become available later in 1943 and then to use the American fleet in a central Pacific offensive, bypassing the Solomons and New Guinea. The delay was also due to the decision to direct 85% of the US war effort towards defeating Germany.
However, Admiral Ernest King, the Director of Naval Operations, successfully argued the need to keep the supply line open to Australia and convinced President Roosevelt, despite the opposition of Army Chief of Staff George C Marshall, that it could be done solely with the Navy and Marines. To that end, the First Marine Division was designated for the operation which began with an unopposed landing on the island on August 7, 1942. The small Japanese force melted away into the jungle. This successful and peaceful start to the operation was not to continue.
On the night of August 8, Japanese cruisers moved down "The Slot" (the channel between the western and eastern Solomons) and sunk three US Navy cruisers and an Australian cruiser. It was the worst surface naval engagement loss in US history. The Navy, concerned about further attacks both on sea and from the air (which the Japanese also dominated) withdrew from the Solomons leaving the Marines on their own. Take a minute and put yourselves in the shoes of a young Marine when the Navy pulled out. The Marines were left with short supplies, limited to two meals a day and then hit with an epidemic of dysentery.
Nonetheless, the Marines and Navy Seabees continued working on the airfield (now named Henderson Field) which was completed on August 20, receiving its first fighters on that day. At about the same time the Japanese began shipping infantry forces to the island in order to recapture the airfield. And most evenings, the Japan navy would be offshore shelling the airfield and the Marines.
[For the account of a now 100 year-old pilot who flew a P-40 fighter from Henderson field see this article . John Thompson received the Navy Cross for his actions.]
Over the next 3 1/2 months five major naval engagements were fought near Guadalcanal with the Americans getting the worst of it early on, including the sinking of the Wasp and the Hornet (from which General Doolittle launched his raid on Tokyo in April), leaving the US with only two other carriers in the Pacific. The final engagements, however, were American victories.
On land during the same period, the Japanese launched two major and unsuccessful attacks on Henderson field and the Americans and Japanese had countless other encounters resulting from raids and patrols.
[To get an idea of what it was like to be a Marine read the Guadalcanal Journal of the late James Donahue which was recently put online by his family. An excerpt:
Again I can thank God for letting me live. We were digging three alternate gun positions in case the Japs break through. We were not given any condition. Suddenly, Fisher spotted 30 Jap bombers just about over us. We grabbed our helmets and ran like hell. Where we were running, I do not know, just trying to get out of reach of the bombers. It can’t be done because no one knows where they are going to bomb. Mugno and I finally spotted a small foxhole and we dove in. Just then we heard them dropping. All the time I was repeating, “Hail, Mary.”]
By mid-December the Japanese decided that Guadalcanal could not be recaptured and began evacuating their forces, completing this in early February.
There were about 7,000 American casualties, including 1,700 dead, during the campaign. In addition about one-third of the Marines contracted malaria. About 31,000 Japanese were killed. A lengthy and very good summary of the entire campaign can be found on Wikipedia.
Guadalcanal was unusual for the Pacific war. The battle lasted much longer than the rest of the island fighting (which could usually be measured in days or weeks), with the exception of the 1944-5 campaign in Luzon in the Philippines which was a much larger island. The battle also provided the first glimpse for the American public of what the war was really like (though it would still be a profound national shock when 1,000 Marines were killed in the three-day battle of Tarawa in November 1943 compared to 1,700 in six months on Guadalcanal). In February 1943, Life Magazine ran a lengthy photo essay on Guadalcanal and its frankness created quite a stir. Below are some of the photos (some are taken from a Daily Mail UK story using the Life photos). You can find all of the photos here.
Marines waiting to be shipped out after four months on the island.
Picture of a burned Japanese head on a disabled tank.
* It is often forgotten now, but America ended up in WWII because of its support of China in its resistance to the Japanese invasion. Our support of China and the 1940 invasion of Indochina by the Japanese triggered the Roosevelt's Administration's decision to embargo sales of oil and other critical materials to Japan. It was the critical need for oil to supply its Navy that triggered the Japanese decision to invade Southeast Asia and seize its oil fields and attack Pearl Harbor.