13994
As the game progresses , the player will be able to unlock an Aces campaign , where they will face off with advanced pilots from North Korea , Iraq , the Soviet Union , and the United States , the four countries the player visits while playing through the first four campaigns .
 North Korea, Iraq, Soviet Union, United States
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 North Korea, Iraq, Soviet Union, United States