Another way of phrasing what you said is doctrines aren't written in stone. But they do impose limitations which should be understood. I will demonstrate this later.
Non superpowers don't have enough nukes to destroy a country. A city or more yes. And that's the deterrence. No one will agree to lose even one city let alone more.
This is a common challenge to the concept of no first use. Especially by those from NATO or Russia because there is no such concept for them. NFU is nonsense as far as they're concerned because by definition first use always was an option and valid action.
But try and think it through. Why does India say no first use in the first place?
Because it leads to conflict stability. If India says NFU. Then China or Pakistan don't have to plan for a decapitating Indian first strike. Because we won't have enough for a second strike.
If one flies, they all fly.
Use that as a trueism to figure out things. So nobody with our doctrine wants to be first.
Back in 2016, directed at Pakistan, the RM said NFU wasn't a given. That is he was introducing ambiguity into NFU.
To me this was nonsense. I was ready to call BS on the RM for the reasons explained earlier. An ambiguous NFU isn't credible. Either you state NFU or not to be credible. It's a binary.
Didn't get much agreement from people to this outright challenge of a cabinet minister.
So why did he say it? Domestic politics perhaps. A way to waylay the opposition. And even to confuse the ones making threats at India from the other side. Playing to their own domestic gallery too.
I was vindicated in 2019, three years later, several months after Balakote, where the PM at the UN stated India adheres to NFU
I gave you the example of the marines in Berlin. That was early 60's. But this applies only to the superpowers.
The first thing to do is demonstrate the weapons are viable through a test or more. This is standard messaging. To then convince the opponent is a gamble. A weak willed opponent may cave. But a more confident one will call your bluff. Then what do you do? Will you proceed with a first strike after what was said above.
Nukes at a minimum are to protect the leadership. If there is no plan to march to Delhi it won't come up. I'm saying in a conventional conflict with China the question of nukes will not come up and it would be foolhardy to try. Since neither of us plans to march to the others capital city.
When you talk about mass you are missing how our doctrine works. Minimum credible deterrent shows you don't need mass to deter. This isn't comprehensible to westerners because they try to interpret through their lens and go wrong. Now if the opponent is fine with losing a few cities then you don't have much deterrence in which case you need to build up the stockpile. Not by a crazy amount but by more than at present.
Also about delivery. Just because India may not be able to reach Beijing does it mean China would be ok with losing Chengdu say. I'm betting no.
Open to conjecture. For the first three weeks they took heavy losses until the US agreed to supply them. If you watch the recent biopic 'Golda', hero of '67 and then defense minister Moshe Dayan was begging her to allow him to use nukes as the IDF was faring badly in the opening stages and her flat no was because the Americans were against.
This also acts in another way. If the Americans didn't get supplies going then Israel would be left with no choice. Saying it was about getting the Sinai back is well and good but who's to say they would stop there and not push on to Tel Aviv. The domestic pressure to do so in Egypt would be immense. What's the contingency plan in that case.
Back off or lose Cairo.
Do you understand why such a threat is credible at a later stage but insufficient to deter the war in the first place.
So you are agreeing then that a conventional conflict against a nuclear non super power is feasible so long as it doesn't go too far. Isn't it.
My point is even a border conflict would be risking a nuclear exchange with superpowers. This is why much effort was made by both sides to ensure the two never came into contact in any theatre. War was possible by proxy only.