The Japanese wanted to get rid of all potential threats. They built up their military and used it to invade other countries for natural materials that they couldn't get from their island country.
The Japanese Path to War
WOW, what a pretty place to take over natural resources.
After the Japanese took over Indochina, FDR stopped all assets with them. He then made an embargo on oil and gas exports to Japan.
FDR "Date Which Will Live in Infamy"
An attack on Pearl Harbor Navy Fleet in Hawaii on December 7, 1941. There were several warning messages sent by the Japanese, but these messages were not given to the commanders at Pearl Harbor. It is still considered a surprise attack with around 2,000 deaths, 20 American vessels, and 300 airplanes damaged.
Appeasement for us! Not for you. The League does what we say, and you should too!
Japan took over Manchuria for its natural resources. When the League of Nations got suspicious of Japan's involvement with the seizing, Japan dropped out of the League. They worked their way into North China and continued to take other countries for their resources.
In FDR's speech after Pearl Harbor, he states "Date Which Will Live in Infamy". He is referring to the attack on Pearl Harbor and how it will be remembered for the damage it did on the American people.
Hitler began breaking the Treaty of Versailles after he became chancellor in 1933. He promised the German people justice for their lost power after WWI. He built up his military, took over the Rhineland, and captured Czechoslovakia. The League believed that their breaking of the Treaty was justified and so they decided to appease Hitler.