1994 Ukraine signed a treaty with Russia and the USA to disarm its nuclear arsenal in return for a treaty that guaranteed Russia and USA would come to their aid if they were ever invaded.
Sorry, didn't happen. Please do not make stuff up. The 1994 Budapest Memorandum on Security Assurances, signed by the US, Russia, the UK and Ukraine was (in return for Ukrainian nuclear disarmament) a "promise" by Russia, the US and the UK not to use force or threaten military or other coercive action against Ukraine. It did not commit any of them to any kind of response in the event the promise was violated or some third party attacked Ukraine. It is not a treaty. There is no enforcement provision. The most it demands is that the signatories "consult" if TSHTF.