The invasion of Ukraine was a contravention of the UN Charter and Russia's international commitments. This is an invasion whether or not any shots are fired. It is also irrelevant that nearly half of the residents of Crimea are ethnic Russian.
The USA and UK undertook in the Budapest Memorandum to guarantee Ukraine's territorial integrity. They are now obliged to provide assistance to Ukraine.
Obama and Cameron have a choice. Stand up to Putin and do their legal duty, which means risking war with Russia. Or do nothing and lose all credibility.
If Obama does nothing meaningful, as he has implied, you can disregard as meaningless any security guarantees that America may have given to Japan. They will not honour them.
Unless Obama forces Putin to back down, America can no longer be trusted to provide you with any security. Japan is now at much greater risk of regional aggression.
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