Don't let history repeat itself. The policy of appeasement failed to prevent war in the past. Putin is a liar and is acting just like Hitler. If someone had stood up to Hitler when he attacked Czechoslovakia and later demanded that the Sudetenland should be absorbed into Germany, Would War II may have been avoided.
It promised to protect Ukraine’s borders, in return for Ukraine giving up its nuclear weapons.The Budapest Memorandum (Ukraine - Memorandum on Security Assurances) was signed by the then-rulers of the USA, UK, Russia and Ukraine – as part of the denuclearization of former Soviet republics after the dissolution of the Soviet Union.
If the U.S. and Ukraine sign a formal mutual defense treaty it would send a strong message to Putin. We should stand by our commitments.