"The U.S. could have refused to elucidate its security commitments to Ukraine, much as it has done vis-à-vis Taiwan for decades. The implicit threat of U.S. and NATO intervention..."

"... would have forced Putin to contend with the risks of further escalation. Instead, Biden granted Putin a free hand. The U.S. also refused to provide advanced weapon systems to Ukraine.... And for those who might argue that Russia would have preempted the shipment of weaponry by invading, I would contend that if invasion was already the predicted outcome, what was there to lose? All the while, the Biden administration failed to pair diplomatic overtures with sufficiently powerful, credible military pressure, perhaps over fears of a bilateral conflict with Russia. These fears were misplaced. I can say from my significant experience dealing with the highest levels of Russia’s military leadership that it has no interest in a bilateral confrontation with the U.S. Russian leaders have zero desire for nuclear war, and they understand that they would inevitably lose in a conventional war. However, Russia excels at compelling the U.S. to self-deter.... Over and over, the president’s longtime senior advisers seem to have recommended narrow, low-risk policy options, and these backfired."

From  "America Could Have Done So Much More to Protect Ukraine/The paths to deterrence were not taken" in The Atlantic.

That's by Alexander Vindman. Remember him?