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The next issue would be the border infrastructure, which currently is massively in China's favor. Allowing us to bring far greater concentrations of troops and equipment to any point along the LAC than India can.
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Yes, the border infrastructure is massively in China's favour, but guess what? They only extend up to the border. No matter how good your rail and road infrastructure in the TAR is, and I will admit that it is pretty impressive, there is no way for you to send large ground formations through the Himalayas. Vehicles, armoured or otherwise, will all be smoked out when they try to make their winding way through mountain passes. And a handful of soldiers defending crucial passes can keep killing as many number of enemy soldiers and vehicles trying to come through.
“Hew down the bridge, Sir Consul,
With all the speed ye may;
I, with two more to help me,
Will hold the foe in play.
In yon strait path a thousand
May well be stopped by three:
Now who will stand on either hand,
And keep the bridge with me?”
In this day and age, with all the reconnaisance assets each side has, it is impossible to send in a large force undetected. As somebody above pointed out, once the mountains are bypassed and the infantry reaches the plains without armour support, they will be mincemeat. So airborne or air assault troops flying over the mountains won't stand a chance either.
All this of course, is in response to the idea that China tries to invade India. It is impossible, and will remain so, unless there is a catastrophic degradation of India's air and ground forces first - like say, complete decimation of all our armour in the plains.
Needless to say, it is also impossible for India to send any forces across into China.
Do you wonder why it is that we are not upgrading our infrastructure to match China's, in the north east? It is not lack of money (we do have enough to build a few roads and rails), or inefficiency. It is because it does not bring enough value for money. For China, it serves a dual purpose of integrating the TAR into the rest of China economically. For us, integrating the north east with the rest of the country is a needed move, but upgrading military infrastructure with border roads and rails does not really serve that purpose. It is far more value for money to raise a new mountain strike corps, and train them specifically for mountain warfare against China - that one corps, if properly trained and employed, can hold off any invasion by China due to the factors explained above. That said, we are massively upgrading some military infrastructure, like airfields and airstrips and radars. Remember DBO.
The Himalayas have always prohibited free movement between the Indian subcontinent and China, which is why these two entities grew as two separate civilizations, and the people look different from each other despite being neighbours. The ability for people to move has increased, but the ability for hostile armies to move has only decreased in modern times.