The Budapest memorandum makes no such Guarantee.

The memorandum concerned Belarus, Ukraine & Kazakhstan.

It’s signatories were Russia, the UK & US.

The points of the memorandum for the 3 nations were:

• Respect Belarusian, Kazakh and Ukrainian independence and sovereignty and their existing borders.
  - Refrain from the threat or use of force against Belarus, Kazakhstan and Ukraine.
  - Refrain from using economic pressure on Belarus, Kazakhstan and Ukraine in order to influence its politics.
  - Seek immediate United Nations Security Council action to provide assistance to Belarus, Kazakhstan and Ukraine, “if Belarus/Kazakhstan/Ukraine should become a victim of an act of aggression or an object of a threat of aggression in which nuclear weapons are used”.
  - Refrain from the use of nuclear arms against Belarus, Kazakhstan and Ukraine.
  - Consult with one another if questions arise regarding these commitments

So…. as you can see… nations were to respect their integrity, but there was never any kind of defence commitment of same.