When I was staying in a pension in Seoul for a month in the autumn of 1967, I tried to speak some Japanese, our only common language, with its 80-year-old Korean proprietor. He refused outright until about a week into my stay, when he gave in and said, "I haven't spoken Japanese since the war and I vowed never to do so again. But you're not a Japanese, so I guess it's all right."
From then on we spent so much time conversing that when I returned to Japan I was speaking Japanese with a Korean accent.
When one country conquers another, as in the case of Japan's colonization of Korea (present-day North and South Korea) in 1910, and then exploits its resources, most of the subject population is deprived of an independent livelihood for at least a generation. If, however, the occupiers also impose their language in place of the native one(s), the subject population may be totally demoralized and deprived of an independent future for generations to come.