This December marks the 29th anniversary of the Budapest Memorandum, in which the United States, the United Kingdom, and Russia provided security commitments to Ukraine in exchange for the latter joining the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) as a non-nuclear state. As part of the agreement, Ukraine relinquished the third largest nuclear arsenal in the world (which it inherited from the U.S.S.R.) and Russia agreed (among other things) “to respect the independence and sovereignty and the existing borders of Ukraine”.
One could question why people sign treaties just to ignore them when it suits