Dear, second or third strike capabilities matter only on paper for us. Surely it will make your enemy think twice but if they are wise enough, they would already be doing that, Tactically, such thing are important for enemies that are far apart, like Russia and America. In our case a second strike capability is not all that fancy as it sounds. If God Forbade, Pakistan launch simultaneous attack on 25 Indian cities (as mentioned in a post above) with nuclear bombs what you think will happen? It will wipe out India but what many people fail to understand or comprehend is what will be its effect on Pakistan?? we share land border, water ways, heck even we share the summer and winter air (monsoon etc) 25 nukes blasting in India will wipe out India but it wont be the only thing these will WIPE OUT!! there will be massive radioactive fallout that will effect Pakistan as well. We will suffer a lot too. So whether India strikes second or not wont be that much important as many or our land will be contaminated with our own nukes already!! Same goes for India. If they drop nuclear bombs on us you can name tens of cities, almost half of India, its western side will be massively effected by the radioactive fallout of there own bombs. Rest of the country will also face consequence!!
Chernobly was an industrial accident, the radio active particles spread out over all or Europe and Western USSR. Here we are talking about specifically designed nuclear weapons, and for that matter, not one or two but 20 or 30 bombs. Imagine what will happen.
In short, nuclear wars are not meant to be fought between neighbors, who ever starts it, even if one of us use them, both of us will be effected and almost destroyed. The whole world will be effected!
These things that we keep on developing are just to ensure that we are not the only one that lose the war. Tactical nukes are understandably important but and all out nuclear war will be MAD, both as a acronym as well as the literal meaning of the word!
Peace!