The correct answer is - oil.
The Japanese Empire, under the rule of Emperor Hirohito, in order to manage to continue with the expansion and gain new territories, needed much more oil than what its supplies where.
The need for oil meant that Japan will attack the places in the region where there are solid amounts of oil reserves, and they did. They attacked and conquered parts of Southeast Asia, and got hold onto the large oil reserves that they desperately needed for their military machinery.
Answer:
Louisiana purchase on April 30, 1803, Texas annexation on December 29, 1845, Gadsden Purchase on December 30, 1853, Mexican Cession on February 2, 1848, and the Adam-Onis Treaty on February 22, 1821
US wanted to get involved because they were concerned about equal access to china via foreign countries
Solution: open door policy 1899
They refused to work with slave traders
