Okay, so a long time ago in the 1940s, there was a really big war called World War II. Japan and America were fighting in this war. At one point, on December 7th, 1941, Japan attacked a place called Pearl Harbor in Hawaii. This was a really big surprise for America because they didn't know it was coming.
Now, some people believe that some leaders in America actually knew that Japan was going to attack Pearl Harbor before it happened. They think that these leaders didn't warn anyone about the attack because they wanted the United States to go to war with Japan. This is called the Pearl Harbor advance-knowledge conspiracy theory.
However, most historians think that this theory is not true. They say that the leaders at the time did not have enough information to know about the attack beforehand. Plus, it would have been a really bad idea to let the attack happen on purpose because a lot of people were killed or hurt.
So, while some people have different opinions about what happened, most experts believe that the attack on Pearl Harbor was a surprise to America and Japan's leaders made the decision to attack on their own.