During what decade did European countries reduce much of Africa, Asia, and the Pacific to colonial possessions? AP World History Chapter 24 During what decade did European countries reduce much of Africa, Asia, and the Pacific to colonial possessions? a. 1860s b. 1790s c. 1870s d. 1850s e. 1840s Answer: C Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+