When the Soviet Union broke up, one of the SSRs of which it was supposedly a Union was Ukraine. A substantial portion of the USSR’s nukes were located in Ukraine.
Not wanting the world to get another nuclear weapons power, NATO and the US convinced newly independent Ukraine to give its nukes to Russia. As a “sweetener” for the deal, we promised Ukraine to protect them from nuclear powers (Russia, obviously).
Francis P. Sempa argues, for RealClearDefense that we owe Ukraine nothing. It is unclear whether he ignores our promise made in the early 1990s, or whether in fact he is unaware of it. He is, of course, correct that if we choose not to honor our promise there is little Ukraine can do about it.
Reneging on our promise would be ill-received in places like South Korea, Taiwan, Japan and Israel to which we have made similar commitments.