How was the attack on Pearl Harbor a Japanese disaster?

Because it brought the USA fully into the war. The full industrial might of the world's foremost industrial power was thrown at it. Worst of all, it didn't just bring her into the war, but it instilled the Americans with anger and determination, leading o an iron will to fight it out. read more

The attack on Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service against the United States naval base at Pearl Harbor, Hawaii Territory, on the morning of December 7, 1941. The attack, also known as the Battle of Pearl Harbor, led to the United States' entry into World War II. read more

Pearl Harbor attack, (December 7, 1941), surprise aerial attack on the U.S. naval base at Pearl Harbor on Oahu Island, Hawaii, by the Japanese that precipitated the entry of the United States into World War II. The strike climaxed a decade of worsening relations between the United States and Japan. read more