India's northeast is a vulnerable point in India's land defenses. While a Chinese offensive into the core of India would be virtually impossible to carry out given the Himalayas standing in the way, China could strike quickly to grab land and then rattle nuclear sabres to get negotiations to ratify their small conquest.
China has claims on territory in this region and has improved transportation networks on their side of the border that give them the edge in moving and supplying troops.
The region also has people perhaps not as thrilled to be in India as the government would like.
Add to this the east-west geographic chokepoint that lies between Bengladesh and Nepal and Bhutan which provides land access to a good sized chunk of India near Myanmar (Burma) and bordering China.
India is planning to build up their troops and infrastructure in the region, But the chokepoint remains.
Now that is being addressed with a land swap agreement with Bangladesh, that also includes this:
Officials said India could offer a $2 billion line of credit to Bangladesh for infrastructure development inside the country.
Ali said Bangladesh was focusing on better connectivity with India by introducing new bus service with Indian states. India faces difficulties reaching its isolated and impoverished northeastern region, and any passage through Bangladesh could cut hundreds of kilometers (miles) to get to those areas.
Along with better relations with Bangladesh, India could gain additional lines of supply to their northeast to reduce the ability of China to interfere with the northernmost routes in time of war.
And the ability to operate securely in their northeast would improve India's ability to strike Chinese anti-ship ballistic missiles that could target waters around India.
UPDATE: Technically unrelated, but operations to the east would be easier to sustain with lines of supply through Bangladesh:
On Tuesday, the Indian army launched a rare cross-border strike against insurgents just over the border with Myanmar, inflicting significant casualties.
If you are able to cross one border, you can cross another.
UPDATE: More on the raid, which was carried out by 70 special forces, it seems. Myanmar was cooperative if not consulted.
And whether or not the message was intended--it was in response to 18 Indian troops killed by those insurgents--Indian commentators are saying it is a message to Pakistan or even China.
I prefer to view it mostly as a lesson that if operations out of the east are necessary, more secure lines of supply to the east are needed. Everyone looks for their own lessons, I guess.