">One persistent U.S. demand is that Ukraine’s territorial integrity be restored. Indeed, the U.S. is party to the Budapest Memorandum in which Russia guaranteed Ukraine’s territorial integrity in return for Ukraine’s transfer of Soviet nuclear weapons to Russia for destruction in accord with U.S.-Soviet arms control agreements. What the U.S. demand ignores is that, under traditional international law, agreements remain valid rebus sic stantibus (things remaining the same).

>When the Budapest memorandum was signed in 1994 there was no plan to expand NATO to the east and Gorbachev had been assured in 1990 that the alliance would not expand. When in fact it did expand right up to Russia’s borders, Russia was confronted with a radically different strategic situation than existed when the Budapest agreement was signed."

And this gives Russia permission to invade a sovereign nation? Ukraine's independence is not just a matter of the Budapest Memorandum, it's a matter of the wishes of the Ukrainian people who have wanted independence from Russia for centuries, something many Russians don't want to acknowledge.

So far, NATO has not invaded Russia or violated its territorial sovereignty but Russia has violated the borders of multiple boarder states, so it's a bit rich for Putin to complain about NATO when he's clearly just trying to reincorporate border states that were conquered by the Tzars.