Most successful military nation ever? Please read details before answering!?

I would say to qualify as militarily successful, a nation has not only to conquer territory, but to hold it over enough time to make it stick and to transmit its customs and culture to others. That being the case, I say (1) Rome and (2) Great Britain. An argument could also be made for China which, despite successive conquests over the centuries, transmitted its culture and customs to each conquerer in turn and served as the model for neighboring states to the east and south.