Ukraine drone strikes in response to Russia Kiev attack

In response to a recent Russian missile attack on Kyiv, Ukraine launched drone strikes deep into Russian territory, targeting Kazan. On December 21, eight drones struck residential and industrial sites in Kazan, causing damage but no reported casualties. This escalation follows a Russian missile strike on Kyiv that resulted in at least one death and several injuries. The conflict intensifies as both sides retaliate with aerial assaults, with Russia also launching over 100 drones into Ukraine overnight.

Ukraine has a lost war. EU Boris engaging in putting ground groups, Zalensky is moving towards total destruction of Ukraine as world watches

What is stopping Russia to use nuclear war heads. None