What were the early warning signs surrounding the surprise attack on Pearl Harbor by Japan?

Answer 1

There were a number of instances right before the Japanese attack on Pearl Harbor. If noticed and followed up with, part of the damage at Pearl Harbor may have been less than it was. Here are some examples of clues that led to Japan's attack:* An intercepted Japanese telephone message gave pause, as it contained questions about the weather conditions in Hawaii and other suspicious items. At this time, the Japanese fleet was 500 miles away from Hawaii. US General Short was informed of this and decided to "sleep on it". He was not sure what the telephone call meant;

* In the early hours of the morning, when the Japanese fleet was 275 miles away, the US minesweeper, the USS Condor spotted a periscope outside of the mouth of Pearl Harbor. The USS destroyer Ward was notified but found no trace of a submarine. Bottom line, nothing was done to truly confirm the sighting. It of course was a Japanese submarine in the wrong place;

* Several hours later the USS Ward spotted the conning tower of a submarine. The USS Ward dropped depth charges on it and sunk the submarine. There a fear that the Ward had sunk a US submarine. At this time the first Japanese warplanes, 230 miles away from Hawaii were taking off; and

* When Japanese warplanes were 137 miles away from Pearl Harbor, US radar picked up a mass of blips. There were so many, radar operators believed their radar was faulty. later on they were thought to be US planes. A bad mistake.