A major factor that allowed imperialist powers to dominate large parts of Asia and Africa in the 19th and 20th centuries was their military and technological superiority. The imperialist powers had developed more advanced weapons, such as machine guns, steamships, and telegraphs, which gave them a significant advantage over the local populations in the regions they sought to control.
Additionally, the imperialist powers were able to exploit political divisions and weaken the existing power structures in the regions they sought to dominate. This often involved playing different groups against each other or supporting local leaders who were willing to collaborate with them in exchange for power and resources.
Furthermore, the imperialist powers used their economic strength to gain control over resources, markets, and labor in the regions they dominated. They established trade networks that favored their own interests and exploited the resources of the colonized countries to fuel their own economies.
Finally, the imperialist powers also used cultural and religious justifications to legitimize their domination, portraying themselves as superior and bringing "civilization" to supposedly "backward" societies. This allowed them to justify their actions and maintain the support of their own populations.
Overall, the military and technological superiority, exploitation of political divisions, economic strength, and cultural justifications were major factors that allowed imperialist powers to dominate large parts of Asia and Africa in the 19th and 20th centuries.