Looking at the terrain map on google maps, I am struck by how much a bowl Assam is with mountains on all sides and how it has factors in favour and disfavour of its defence. The biggest disadvantage I see is how the borders of the neighboring countries are drawn.
Are you ready for this? Are you sitting down? They were never drawn.
OK, that's an exaggeration.
The India-Tibet border was never drawn. If you want a detailed account, I will have to publish it elsewhere, and inform you where to look.
Looking left and right:
The boundaries with Bhutan were clearly established both because Bhutan became a state within the British sphere of influence very soon, and the Bhutanese themselves built strong links to India; close to where I stay in Calcutta, there is an enormous multi-stored condominium, one of the best and oldest in Calcutta, still a hugely fashionable address, something like the Watergate Complex, which was jointly developed by two Calcutta entrepreneurs and the Bhutanese. They winter here, or rather, take off from here for their winter expeditions. All the senior bureaucrats and policemen were very well treated in Bhutan, and it is difficult culturally to be hostile to the Bhutanese. So the border demarcation was smooth and painless; whenever they wanted an adjustment, they got it.
Sikkim, ditto. It was divided between two quasi-royal families, the Chogyal and the Kazi being head of the two. In historical times, it was the cockpit of the Himalayas, and was fought over by Bhutanese and Nepalese and Tibetan. At one stage, it was a tributary of the Qing, as much as Tibet was. In the late 19th century, it succumbed to British pressure and became a British protectorate, independent but under suzerainty, like the princely states of India. In 47, it was mysteriously allowed a choice, which no other princely state was, and the referendum which followed left them under Indian suzerainty but separate. At this stage, the Chogyal had an American wife, a real public relations problem of major, major dimensions; just to balance him, the Kazi was married to the niece of Field Marshal Mannerheim. The Finns won; the Chogyal was removed by popular pressure, not without the deft guidance and management of the Kazi, who continued in power as an elected representative for the rest of his life. Here, too, being so close to the hill station of Darjeeling, the dimensions are absolutely clear.
Myanmar borders were absolutely unclear. In three campaigns, the British took over Burma in the 19th century, sent the last Mughal emperor to Burma to live out the rest of his days, balanced this by sending the last Burmese king to Maharashtra to live out the rest of his days, and ruled Burma under the identical same bureaucracy and police service as the rest of India. The most famous Burmese policeman was Eric Blair, who resigned and went back to England to become a famous writer, under the nom de plume of George Orwell. Since the bureaucracy was one and the same, boundaries were established very, very clearly, but there are large tracts which are just lines on the map, there being no geographical attribute to mark the separation. It is quite possible to contemplate villages in all the border regions straddling the boundary. Since these borderlands are inhabited by rebels against both states, neither side wants to grasp the nettle too firmly, not just yet. In some Burmese border areas, not the ones next to Yunnan that we are both looking at with such fascination, the border regions keep Chinese time and use Chinese currency. As you may imagine, this is not very amusing for New Delhi to contemplate.
Bangladesh was India until 47, so not much problem with borders but for the enclaves and for Berubari. Leaving Berubari aside for the time being - unless you have 72 undivided hours to spare - the problem of the enclaves is the problem of the dratted princely state of Coochbehar; it was ruled by a tribal dynasty, which fought off the Mughals and the Ahoms alike till they succumbed to the vastly greater resources against them and accepted the sovereignty of the Mughals. Their land holdings were in penny packets near the borders of their state, as is usual in feudal land-holdings. Now the partition on this border gave the whole of the state of Coochbehar to India, so Coochbehar's enclaves outside Coochbehar went to India, while the surrounding territory in these couple of hundred cases went to Bangladesh - Pakistan that was. And similarly, there were bits of Bangladesh in India (Coochbehar). Apart from this, no serious issues.
I am not quite sure what is this. Are we talking about the PLA or the IA? (Sorry I'm dense)
*I also had to look up the reference to the six men of Hindustan lol.
The IA; look up dispositions of III Corps and IV Corps (both under Eastern Command).
I sincerely hope you and others are enjoying this exchange.