Tac nuke will ofcource will not be launched at the first site of the enemy they will used incase certain thresholds have been crossed , the thresholds vary in diffrent situations
Incase Pakistan has to use Tactical Nuclear weapons , and India decides to retaliate massively, it will be met with a massive retalliation from Pakistani side too,
and i bet New Delhi knows that there will be no winners in this nuclear exchange ,
So my guess is India will not retaliate massively, because ''No one'' wants the subcontinent to become a nuclear wasteland.
so what will New Delhi do?
- Withdraw it's troops?
- Respond with a tactical nuclear strike?
In the former case it will be stupid to think Pakistan won't respond
Don't you think it will lead to an uncontrollable exchane and a massive nuclear exchange ; eventually?
Won't it be better if Indian troops didn't cross the border in the first place?
Now apply that logic to the other side as well. Pakistan knows that if it uses tactical nukes, the retaliation will be massive, and possibly the counter retalitation as well. Islamabad knows there will be no winners in such an exchange, so would they really use nukes (tactical or otherwise) on an Indian division, simply to prevent the capture of some border territory?
India's case is quite straightforward - we will not initiate nuclear war, but if the other side does, we will make sure that we will go all the way.
Now I want you to think carefully and answer your own question as to what India would do, if Pak used a tactical nuke on our troops. One of the choices you gave was India withdrawing its troops. You really think that ould happen? That India will send eight IBGs into Pakistan, and as soon as Pak uses a tactical nuke, we would accept defeat, withdraw our troops and start a new life? Sorry, that's not going to happen. If our soldiers are nuked, there will be no choice for us but to respond massively. That's the shallow pakistani internet warrior's way of thinking, that as soon as a Nassr is used, India will simply accept defeat and go back. I'm sure Pakistani soldiers and generals know better than to underestimate Indian willpower to such an extent. Only a non nuclear country will behave in that manner, not a nuclear one with massive conventional superiority and enough nuclear wepaons to end it all. There will be massive counter nukes on Pakistani troop concentrations, airfields and cities, and several more Indian divisions will march in. From then on, even if there are no winners, there won't be situation where Pak can simply sit back and say "Our Nasr thwarted India". Nasr is no silver bullet, and in fact there is no such silver bullet that can completely nullify massive military superiority, unless you have some technological advantage that the other side doesn't - like USA and Japan in WW2.
You should understand something - India's aims have never been to invade and conquer Pakistan - indeed, what would India do after such a deed, even if it was possible? Pakistan is a separate country, and we are far better off keeping Pakistan separate. Our aim has always been to make sure Pakistan does not take our territory, by hook or by crook. It is Pakistan that has initiated all the Kashmir wars (including the latest one at Kargil) to take Indian Kashmir. India has never tried to take Pakistani Kashmir or Punjab or SIndh, and has no desire to. So this talk of "certain thresholds and red lines" by Pakistan, by which they mean if the very existence of Pakistan being threatened by a foreign power, is never going to be reached. India is never going to try and march into Islamabad, because what exactly are we supposed to do after that? Rule Pakistan? India has two aims in a potential war - 1) If Pakistan attacks us conentionally to take Kashmir again, then prevent that from happening, as we have always done. 2) If Pakistan is a nuisance and keeps doing "non state actor" terror acts like the parliament attack or the mumbai massacre, then do punitive strikes on Pakistan to extract some form of agreement or concessions from Pakistan. In the past we have had only mixed succes on that front. We couldn't do much after the mumbai massacre, but when the parliament was attacked, and we launched op Parakram, we were able to get Pakistan to agree to a ceasefire on the border for the first time, which has held to this day, which means Pakistan de-facto accepting the LoC as a border.
Now all this talk about India's plans under the nuclear umbrella is in continuation of this, and to be launched in case of another scenario (2) described above. We would try to caputre some territory or make minor intrusions from eight different axes, and force Pakistan to come to the negotiating table from a position of weakness, without crossing the red lines.
But if Pak decides to press the nuclear button even for that, well, that's where the massive retaliation part kicks in.
All said and done, India will not atttempt to threaten the very existence of Pakistan. It will be Pakistan's choice whether to go down that road, dragging India with it. Whether the complete destruction of both countries is a fair price to pay for small intrusions, is something Pakistan will have to figure out. The very fact that they talk about the existence of red lines tells me that they know the answer.