How did the japan avoid detection?

The Japanese enforced radio silence for about a month before Pearl Harbor. This meant that they turned off all of their radio communications to prevent the Americans from receiving any messages.

Weather Station on Hawaii

The Japanese established a weather station in Hawaii in the 1930’s. This station provided important weather information that was used to plan their attack.

Submarine Reconnaissance

The Japanese used submarines to scout and recon Pearl Harbor in the weeks leading up to the attack. These submarines were able to gather important intelligence about the harbor defenses.

Aerial Reconnaissance

The Japanese sent over 100 aircraft to scout Pearl Harbor in the weeks leading up to the attack. These aircraft took many photographs of the base, including the locations of the American ships.

Deception

The Japanese used a number of deceptive measures to fool the Americans. For example, they sent a radio message that made it appear that their fleet was moving in a different direction.

Timing of the Attack

The Japanese attacked Pearl Harbor on a Sunday morning, when most of the American soldiers and sailors were either asleep or attending church. This helped reduce casualties.

All of these factors combined to allow the Japanese to successfully avoid detection until they were already attacking Pearl Harbor.