Pearl Harbor was the result of a culmination of events in the Pacific. Deteriorating US-Japanese relations in the period from 1931 to 1941 put the two nations on a path to war, which started at Pearl Harbor.
In 1931, the Japanese military occupied parts of China. A larger scale invasion of China in 1937 followed the invasion of Manchuria. Japan's army captured expansive territory, but could not win that war.
When the League of Nations requested Japan withdraw from Manchuria in 1933, Japan withdrew from the League. Of course, the USA never joined the League of Nations and played no part in it.
However, there was an US economic response to Japanese actions in China and Indochina by 1940. The United States established trade sanctions, and Japanese oil supplies became limited consequently. Japan began to feel the burden of such sanctions, and as such planned to launch an airstrike on the US naval base of Pearl Harbor.
Both sides considered a war between the Japan and the USA increasingly inevitable. Of course, the Japanese were certain that their planned strike on Pearl Harbor would result in war. America suspected that a spark of some sort might develop.
How exactly Japan would engage the USA was something that US intelligence never accurately deciphered. Japanese military strategists began Pearl Harbor planning in earnest from 1940 onward. Inspired by the British at Taranto, the IJN sought a surprise strike at Pearl to knock out the naval fleet stationed there.
By doing so the Japanese would have, at the least, a temporary naval advantage and be able to capture the European colonies in the region. As such, with plans finalized, the Japanese strike force set sail for Pearl in late 1941.
The US warning systems did not adequately detect the fleet heading for Pearl. American radar detection of the fleet's aircraft was passed off as US planes due to arrive, and a submarine sinking was routinely handled. Kimmel needed verification of the detected minisubmarine.
As their fleet moved towards the target, the Japanese made diplomatic moves. A declaration of war, or something approaching it, was written before the strike. Japan was going to present that to the USA shortly before the raid - but the transcription delayed it.
Japan approached Pearl Harbor with a fleet of six aircraft carriers. In addition to this, approx 400 planes were available to bomb the harbor, along with escorting battleships and cruisers. Five minisubmarines also supported the raid, but they had little impact.
The IJN organized the airstrike into two waves. Japan organized the first wave for the primary targets such as battleships and airfields. Then the IJN planned to launch secondary attack for any other objectives that may have remained.
Before the IJN launched the first wave, the Japanese launched reconnaissance planes to scout over Pearl Harbor. Two aircraft scouted over Oahu to report on the fleet location.
Hereafter, the IJN launched the first wave on Pearl Harbor that approached the harbor undetected by America. They were able to strike at American battleships at Pearl, and a second wave that bombed the ships California, West Virginia and Oklahoma followed.
By the end of the airstrike, Japan had sunk four American battleships and two cruisers. In addition to this, 188 US aircraft were lost. The airstrike had damaged further ships and aircraft, but the U.S. Navy repaired some of them after Pearl Harbor.
The IJN had also planned potential third wave. That wave was to target American fuel depots and naval yards. However, the IJN never launched the third sortie and withdrew. That might have been down to potential fuel shortages or to cut back potential losses of further planes.
Japan's operation was effective and met the foremost objectives. However, American fuel depots remained in place, while the U.S. Navy was also able to repair some ships and raise the Oklahoma. U.S carriers were not stationed at Pearl Harbor when Japan struck.
Hereafter, Japan and America were at war. While Japan had not given an official war declaration prior to the airstrike, it was given after the approach and attack on Pearl Harbor. Pearl Harbor was a tactical victory, but that was as good as it got for Japan.
With the fires still burning, the casualties and losses had to be counted. Starting with the ships, America had five battleships sunk along with two destroyers and a further three battleships and cruisers damaged. The raid had destroyed 188 aircraft with 155 damaged. Personnel losses were recorded at 2,345. The Japanese only lost 29 planes and 55 airmen.
Such losses deprived America of battleships, although its four carriers remained intact due to being out of harbor at the time of the raid. The fuel storage at Pearl Harbor was also intact.
Salvage operations were also carried out after the raid. Within six months five battleships and two cruisers were either patched up or re-floated. Although the Utah and Arizona could not be repaired, the U.S. Navy restored a lot of their equipment for other vessels. In light of this the damage done at Pearl Harbor was not entirely extensive.
The Robert's Commission was also set up to investigate the Pearl Harbor raid. It concluded intelligence and warning systems were to blame. Although its findings have been open to question since.
America was now at war with the Japanese Empire and the European nations of Germany and Italy. The airstrike galvanized the country; although an immediate counter-strike was not delivered. America began to produce armaments and war material more readily, and it would not be too long before the effects of this would be felt.
Japan used the time it had brought effectively. In 1941 and 1942, the Japanese military began to capture European and American colonies, drawing them close to New Zealand and the Australian mainland.
America began light-scale air raids on the Japanese mainland such as the Doolittle Raid. However, it was not until the Battle of Coral Sea that the Japanese and American navies would confront each other. Here losses were relatively equal.
However, at the Battle of Midway America destroyed four IJN carriers. Japanese aircraft and personnel were also lost in the battle, and from here on America were on the offensive. The U.S. Navy lost the Yorktown, but it was still a fantastic triumph.
As such, the effects of Pearl Harbor were not too serious for America after all. In the aftermath the American navy recovered quickly enough to confront and defeat the IJN naval forces in 1942 and 1943, while its army began to recapture the lost territory from 1943 onward. This trend continued up until 1945, when the Japanese surrendered.