Imperialism began in the 19th century and continued into the 20th century as powerful nations like the UK, France, Germany, Italy, Japan, and the US extended their rule over other countries and built large empires. Key figures who advanced imperialism included Cecil Rhodes, Theodore Roosevelt, and William McKinley. Significant events supporting imperialism were World War I and World War II, while the Opium War weakened China and allowed Britain to gain economic and political control. While imperialism spread technology and fueled industrialization, it also exploited resources and denied rights to colonized peoples.