Just a note that broad questions like these generally get taken down by the mods. You might hold this until Friday's Free-For-All thread, or try to ask a specific question (like, say, "Was the overall impact of the opening of Japan positive for the average Japanese citizen?" or "How did the Roman Empire treat tribes that surrendered instead of fighting?").

Are you asking about a specif instance where two civilizations merged together peacefully without lowering the less advanced one's class and status in that new society, or are you inquiring when a lower advanced civilization was able to fend off a higher advanced civilization from invasion?

This submission has been removed because it violates the rule on poll-type questions. These poll-type questions do not lend themselves to answers with a firm foundation in sources and research, and the resulting threads usually turn into monsters with enormous speculation and little focussed discussion. “Most”, “least”, "best" and "worst" questions usually lead to vague, subjective, and speculative answers. If you'd like, you may PM /u/caffarelli to have your question considered for an upcoming Tuesday Trivia thread.