Answer:
The Japanese invasion of Manchuria heightened tensions in Asia, making Japan a focus of Western nations in the coming war.
Step-by-step explanation:
It is the obvious answer. While the international focus was maintaining piece, the Japanese began a war. Invasions will never be easily tolerated and there will always be countries strongly against it. In that era, specifically, it caused greater problems since Asia was already tense and it didn't become any better with the invasion. Sanctions was too little for what happened.