It was one thing for the U.S. to drop two atomic bombs on Japan, when the latter was clearly militarily defeated, and at a moment in history when nuclear weapons had never been used before in war and no one else had them.
Regardless of the wisdom or lack thereof, the results of the Hiroshima and Nagasaki bombings were clearly horrifying. Hence why nuclear weapons have never been used offensively by any nation ever since. That includes wars fought by both the U.S. and USSR that resulted in “losses” (Vietnam, Afghanistan). And including, notably, the Korean War just a few years after WWII that was fought to a bitter draw — when Truman, the same President who ordered the Hiroshima/Nagasaki bombings, was still in power.
Hiroshima/Nagasaki therefore did not create a “precedent” in favor of dropping nukes, as Putin claimed in a rambling speech, but rather serves as an “exception that proves the rule.”
The nuclear taboo has held for decades. Putin’s military debacle in Ukraine doesn’t justify breaking it whatsoever. Further, there is no feasible way for Russia to use nukes in Ukraine in a tactically beneficial way, without exposing his own troops and civilians to radioactive fallout. Doing so would also invite a massive NATO conventional, and possibly nuclear, intervention on Ukraine’s behalf. Putin’s regime, already teetering, would crumble.
So, he won’t.
If I’m wrong, and Putin does so anyway, then the fault and the consequences will be entirely on him.