For that you've to understand geography...
First you need to understand,why China unilaterally made ceasefire?Because for isolated bases in Arunachal Pradesh,Chinese Human waves(this form of warfare was PLA's primary tactics in 1950s and 1960s) was effective.But PLA didn't have any strength to cross mountainous regions of Arunachal with heavy weapons and armors to wage war in plain.In fact,they still lack this skill due to Indian Govt's (stupid) plan to keep that area underdeveloped.
Even today,waging a land war is easy in Arunachal,but they can't effectively back it with Airpower and there is no way to bring armor into the picture. On other hand,India can make effective airpower use in Arunachal.Thats why China uses Salami tactics now to capture small portion of land and hold it(encroach),they don't go for open war.
For details,you should read why "Flying the hump" was so dangerous...
https://en.wikipedia.org/wiki/The_Hump