Because US and UK blockaded supplies to Japan since they protested Japanese Empire's expansion into Asia like UK and US were. The two sides tired to use diplomacy to solve the differences, but Japan bet everything they had to risk war to destroy all of the US Pacific Fleet in Pearl Harbor.
The real reason for Japan's attack (on the US, the British Empire & the Dutch) was the Japanese Army's obsession with their on-going brutal conquest of China. The United States had been taking diplomatic and economic steps against Japan for several years to convince (or force) the Japanese to end their war of conquest in Asia. The Japanese Army actually controlled the Japanese Government since the early 1930's. The Japanese Army refused to end its war of conquest & extreme brutality in China.
Beyond China, the Japanese Army had plans to take advantage of the weakness of the British, French, Dutch & Soviet Union in Asia because of Hitler's conquests in Europe. The Japanese wanted to be free of American interference, and create a vast Asian empire that would have eventually included China, eastern Siberia, Mongolia, Korea, Formosa, Indo-China, Thailand, Burma, Malaysia, Indonesia, Borneo, Sumatra, Java, Philippines, Guam, Wake Island, & New Guinea; and possibly India.
The Japanese military thought that the best way to keep the United States from interfering in their plans in Asia, was to deliver a surprise attack on various US bases throughout the Pacific to do as much damage to the US Military capability in the Pacific. At Pearl Harbor, they intended to sink as many battleships, cruisers & aircraft carriers as possible. At Manila they intended to follow-up with an invasion and capture of the Philippines. At Wake Island they intended to seize the island. The Japanese also attacked the bases, ships & troops of the British Empire. All this was intended to persuade the United States & Britain to negotiate a settlement giving the Japanese most of the western Pacific territories, and most of Asia. They hoped that the US & Britain would not want to fight a prolonged & costly war in Asia to liberate what territory the Japanese could capture in the first six months of the war.
Expanding on the issue of imperialism & colonization from the first answer: Although the Japanese were jealous of European imperialistic efforts in China, and they publically claimed that they wanted to force the Europeans & Americans out of Asia (for the good of Asia), they in-fact were much more brutal & lethal to Asians than the Europeans & Americans ever were. In the 20th Century, the Americans, British, Portuguese and Dutch had begun to improve relations with Asians. This effort was lead by the US. The Philippines was placed on the path towards independence by 1946. The United States leaders criticized European imperialism in Asia. Europeans began to listen. Later, during the war, where-ever the Japanese occupied an Asian nation, that nation soon turned for assistance from the Allies & resisted the Japanese. By the time that war came to the Pacific, the Americans & most European colonial powers in Asia had significantly improved the situation for the populations in their territories & colonies. The situation was just the opposite in Japanese occupied areas of Asia. Japan had absolutely no "moral high ground" from which to dictate to Americans & Europeans. Fortunately-much has changed since (and because of) the war. Relations in Asia towards the Japanese have improved because the Japanese have changed their focus from military conquest to economic development/competition.
Expanding on the issue of diplomatic negotiations prior to the Japanese attack in December 1941:
The Japanese diplomatic position never waivered from that of demanding that the United States accept the Japanese conquest of China and that the United States should not interfere in Japanese military actions. The Japanese wanted economic sanctions, against them, lifted by the United States, but offered nothing for it. Negotiations were doomed to fail, except that a small group of misguided intellectuals (American clergymen & some Japanese business interests) provided false & misleading information (about Japanese diplomatic positions) that lead to false hope in a diplomatic compromise. By 1941, the Japanese government secretly undertook to use the negotiations as a delaying tactic, while preparing & planning for war. Even the Japanese negotiators in Washington, DC were not told of the futility of their efforts.
Pearl Harbor .
The United States and their ally, the British Empire, declared war on Japan December 8, 1941. This declaration was after the attack on Pearl Harbor.
December 7, 1941 (December 8 in Japan) that led to the United States' entry into World War 2
The United States declared war on Japan.
The attack of the United States by the Empire of Japan on December 7th, 1941 brough the US into WWII which benefitted Britain.
The American Fleet was anchored in Pearl Harbor, Hawaii. The Japanese bombed Pearl Harbor on December 7, 1941. It was a surprise attack. The United States declared war on Japan. It caused the United States to enter World War 2.
Following the attack on Pearl Harbor on December 7, 1941, the United States declared war on Japan. Because Germany and Japan were in an alliance, Germany then declared war on the US. The United States, in turn, declared war on Germany.
On December 8, 1941, following the attack on Pearl Harbor, the United States declared war on the Empire of Japan. Following the U.S declaration against Japan, Germany and Italy declared war on the United States.
There are several reasons why the United States was unprepared for the attack on Pearl Harbor. The greatest of these reasons was the United States and Japan were working out a non aggressor treaty. The United States also did not expect an attack to occur on a Sunday.
BECAUSE JAPAN DIDN'T DECLAIRE WAR ON THE UNITED STATES SO THEY WERE NOT PARPARED. AS A RESAULT OF JAPAN ATTACKING PEARL HARBOR THE UNITED STATES DECLEARED WAR ON JAPAN.
In December 1941 Japan attacked the United States forces at Pearl Harbor, Hawaii, which pulled the United States into war.
Japan, Attack; United States, Victim
Japan attacked the United States
Three words. IT'S ON *****
The United States declared war on Japan on December 8, 1941, one day after the Japanese surprise attack on Pearl Harbor, Hawaii.
The attack of Pearl Harbor was inevitable. the United States were cutting back on oil supplies from the Japanese in return was retaliation of Japan. Knowing of the attack on pearl harbor maybe but going to a no. An attack on the United States from the Japanese, yes because of retaliation.
In December of 1941, following the attack on Pearl Harbor, President Franklin D. Roosevelt asked Congress to declare war on Japan. Congress agreed and the United States was at war with Japan.
The United States declared war on Japan December 8 , 1941 .
It was the FDR speech on 8 December, 1941 in which the United States declared war on Imperial Japan following the attack on Pearl Harbor.
The United States declared war on Japan on 8th December 1941, the day after the Japanese attack on Pearl Harbour.
The United states, more or less tried to ruin the Japanese ecnomy and forced the japs to attack to get the supplies they needed. America knew about the attack, and was looking for a reason to get in the war.
December 8, 1941.
The United States declared war against Japan on December 8, 1941, the day after Japan's attack on Pearl Harbor, Hawaii. Three days later, on December 11, 1941, Germany declared war against the United States.
The United States declared war on Japan the next day, December 8, 1941 (Washington DC time).