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, during which European empires grew their armies and resources by conquering colonies. While imperialism spread technology and fueled industrialization, it also exploited resources and peoples, denying rights to colonized nations.